Although at odds with classical literature and popular myths, designing new and useful things is mainly a process of the continual improvement of an initial something that only a mother (or inventor) could love. This developmental road is long and bumpy, with more 'next great things' crashing out than winning through, and even those that eventually make good may have little resemblance to what they looked like on the start-line.
Features of today's car are barely recognisable in Benz's 1885 patent-motorwagen.
Early cell phones had more kinship with a brick than with an iphone.
And where's the Jetsons aircar, expected momentarily since the 1960's, or the fuel cell that was first predicted to make fossil fuels but a quaint byway of history before 1900?

1 Skin 76
in strong wind.
1 Skin 76
with lever bridle.
1 Skin 77 with uncoated fabric rear section
6 sqm 1 Skin with adjustable bridle in stronger wind.
But improvement doesn't stop happening when a new thing finally establishes itself as useful (the Model T moment). Tin Lizzies changed the world in 1909, but are undrivable by comparison to any modern car.
From when fundamental elements are established, designs tend to get inexorably better, and cheaper- without any apparent limit.
Consider the wrist watch; 300 years ago they didn't keep good time, needed winding every day, were as fragile as a butterfly, and cost more than a house. Any $10 watch today is superior in every way- except re-sale value.
But very occasionally, a design comes along that is better than later 'improvements', sometimes for years.
The classic example of this has to be the AK47 (Soviet era assault rifle), which, after 70 years in a fast changing industry, is still the weapon of choice for most of the world's baddies (whose judgement in this matter can scarcely be questioned).
Another is the 1995 24 valve diesel Toyota Landcruiser VX. After 20 years during which motor vehicle technology has advanced rapidly, their resale value consistently exceeds that of similar vehicles half their age and 1/3 their kilometres. $35,000 for a 1995 VX with 400,000km on the clock anyone? We'll yes, and count yourself lucky to have found one.
The Douglas DC3 C47 "gooney bird" ranks with the AK and the VX , as does Lister's 1929 CS6 single cylinder diesel stationary engine, which is still in production (as copies in Iran and India ) after 80+ years.

And in the kite world? Are there any designs that have endured?
That I can think of, except for the Flexifoil and NASA wings, there are no designs dating from the origins of modern traction kiting in the 1980's that are still useful- and the Flexifoil is barely a traction kite, while NASAs from back then do not bear comparison with current offerings. I did a 'foil design, the NGEN, in the late 1990s that remained competitive in buggy racing through to 2010 or so, even though it had been superseded by new models a number of times, but this was just a lucky accident- and NGENs were always a bitch to fly. For single line kites, I'm sure there are some; our original single line Octopus from the late 1970's is as popular as ever. We've now provided 3 generations of the same family with these; granny says "there's nothing much wrong with my one or my daughter's, but I'd like to get a new one for my granddaughter".
But anyway, thinking about this general phenomenon, and having good wind, time to for testing, and the incentive of a raft of upcoming events, during the last month I've gone back to some of the 80 different single skin pilot kite prototypes built during the last 3 years, to see if anything useful has been overlooked.
Two things:
The wind speed at which they begin to exhibit superstability (a tendency to occasionally dive off inexorably to one side or the other) has stayed pretty much constant at around 40km/hr during this period. Some Boomers and 1Skins have flown successfully in much stronger winds, but don't stay in tune from one day to the next, nor even necessarily from one launch to the next. This is useful rather than depressing information because it suggest that insufficient restorative moment (the kite's ability to recover after being tilted to one side), rather than skin and leading edge distortions (which I'd been concentrating on until now), may be the prime driver of superstability. This refocus has already born fruit in an all new lower aspect ratio single skin pilot called the SInger (restorative moment is an inverse function of aspect ratio). Singers are 2.25sq.m, have 4 cells and 16 bridles- and sometimes a tail (whatever works- for now). They have similar pull but fly at a higher angle than conventional 8sq.m ram air pilots and handle strong winds much better than the higher aspect ratio 5 cell (1Skin) or 7 cell (Boomer) styles.
The other discovery is that one particular kite, a 2015 43 series scaled to 6sq.m, is the best light wind kite I've ever seen, bar none. About a year ago I fitted adjustable bridles to some ISkins for light wind flying. For the 6sq.m, this is an up to 120mm shortening of the front four bridles, at which setting their minimum required wind speed is less than for conventional ram air pilot kites. Best of all, even by say 10km/hr, they have enough lift to hoist significant show kites into the sky- in contrast to a conventional 12sq.m ram air pilot kite that can barely lift itself at this wind speed. What I've only just noticed, is that for this particular kite, as wind speed increases, the centre leading edge collapses before the shoulders push in, extending the range for each setting. This kite does < 8km/hr to >20km/hr for the lightest wind setting, making it entirely practical for kite event flying.
With these discoveries, I've now gone over, maybe a bit prematurely, to single skin only shows- no ram air kites at all. Being able to take more kites to events within the same baggage allowance is a bonus.

Flying 4 Skins in Delhi
Jan 2017.
Singer 22 5sqm single skin pilot kite.
with tail.
SS Octopus
Wakanui 1 May 2015.
And while this had been happening I've also been having a tremendous tussle with the serpent version of the single skin octopus. Since early 2016, the octopus versions have been flying well, with excellent stability across a wide wind range (albeit requiring 3 different bridle settings in total). In many festival circumstances, I now use the 20m single skin octopus as a pilot kite (and at just 2.7kg they are barely heavier than a large conventional ram air pilot while being a substantial show kite in their own right). For some reason the serpent version (same head and bridles, same area and weight of tail) will barely fly. After so many re-sews of the head/tail area that the fabric is falling apart from needle holes, one did begin to fly OK. But the first time I saw it side on (in Delhi 2 weeks ago), sent me back to the cutting floor, because a scoop effect contrived to spill some flow and get needed drag just below the head, was too unsightly, even for me (I know, I'm supposed to be the god of ugly, must be losing it, hope Andrew Beattie never reads this). There are plenty of less form-distorting things to try yet though, and a strong incentive in that a single long tapered tail doesn't snag on things and people like the linked tentacles of the Octopus do. When the Serpent is flying satisfactorily, I'll start working on some of the very many other show designs that are obvious candidates for single skin format: Chinese opera masks for example.

Significantly, stacking is now also working pretty well for the single skin range- which is useful in the limited sky space at most kite events. Stacking reliably requires the top kite to fly at a higher angle than lower kites. To this end, latest model 1Skins (after #76) are usually the only satisfactory pilots. These (and Singers) are not yet commercially available, but I often have spares with me at events. An exception is the above mentioned 2015 43 series 6sq.m 1Skins for winds under 25km/hr. When stacking it's also useful to set the lower kites at a higher wind setting than if they were flying solo, so as to reduce overflying.

43 series 1Skins (including the 6sq.m's), and the single skin Octopus are available ex Kaixuan: Revolutionary Single Skin Pilot Kite. I'm not yet pushing sales, by the theory that every few months is seeing significant improvements- even if of the 2 steps forward one step backwards type, that is a characteristic of this development stage.
But single skin kites of all these types are now getting past the pink, wrinkly, demanding of constant attention, phase that only a mother and a few dotting aunts can love!