One note on this:
The reason gliders are so extremely high AR, is not really to achieve more lift, but to achieve higher glide ratio.
Higher AR means less drag especially when flying at high lift, but not really more overall lift - so when soaring in a thermal bubble you dont need the high AR as even medium AR wings has about the same lift, but when you have to cover a distance between thermals where you are losing height (no lift maybe down-lift) you want the absolute maximum glide angle and speed.
Also, the glider competitions are usually about covering as much distance as possible in the shortest amount of time - thus again, max glide ratio and speed (low drag) needed.
On a sidenote, the reason why gliders have ballast in the tanks, is because the heavier it is, the faster it can cover a given distance (especially important in head-wind), and the glide ratio when no wind is exactly the same whether it is light or heavy.
Many do not know this.
The sink rate though, increases a lot, the heavier it is.
Back to the topic - our hydrofoils got so low AR, that increased AR gives you a bit more overall lift, yes.
But not much difference, compared to what sheer size and camber will give you.
Glide ratio and low drag (speed) is much better on high AR wings though, which IMO is very important when you ride with big powerspike foil kites, where the apparent wind has much more effect than on other kites.
But for "normal" smaller kites sheer wing size and camber is almost the only determining factor to how early you can start IMO, as Gunnar says too.
Higher AR on huge wings will still go a tad earlier, but also turn lousy and stall more rapidly (eventhough it doesnt matter much I think when so big)
PF
