lovethepirk, I still hold on to my statements not in doubt.
Here is why you might have a different view:
7-9 knots is not weak/marginal wind, at 7 knots I can ride with medium AR tubekites 12 m2 (I can at 78 kg) with a bigger wing, preferably a bit higher AR than the surf wings, but these will work also.
At 9 knots I could just get away with a 9-10 m2 kite no problem (long lines of course).
It is when you go lower, the really forward flying foil kites are the only ones that can work IMO.
Yes, as you write, they can stall easier and require a really good pilot.
Even the very best racers struggle somewhat with the latest high AR faster flying (thin profile) racekites, as they are soooo sensitive.
BUT, when you can master this, they go beyond what one would think possible!
Apparent wind is what it is all about when you go below 6 knots, and here the angle get pinched so much, that you need high AR forward flying kites, in order to ride, impossible otherwise IMO.
The amazing part is, that they can go at incredible speeds, but this is ONLY due to the higher AR wings and kites.
This speed gives you apparent wind and as the pull is squared with the speed, it means a lot - but still bear in mind it is not as effective because of the pinching effect.
One can also say, that as long as you dont have issues with being too powered, the lower AR kites are A LOT easier to fly, which is why many think they are better.
And maybe they are, for the individual, true.
But IMO it is lousy technique
Just like someone riding a high AR foil kite for the very first time in light wind, what happens?
Kite is dived and pulls like a maniac, you get a fresh aggressive waterstart
Now kite is low, in low winds, you are not foiling yet, and it loses ALL power, so you fall backwards ha haa - that is what happens with each and everyone I have seen (including myself many years ago)
With the right technique though, these kites are unbeatable in terms of lowend in my experience - and that was the question indirectly I assume, and as high AR foil kites fly the furthest forward in the window, and high AR tube kites flat profile quite far forward, high AR tube thick profile a bit lower, low AR tube flat profile even lower usually, and low AR thick profile the lowest, it is somewhat also in this order the lowest weak/marginal wind limit is.
BUT, bear in mind, the most forward flying kites require a better rider/pilot indeed, and the deeper they fly in the window, the easier they are (as long as we dont talk about too much power)
Personally as a "non racer" I prefer LEI kites as soon as possible so from 7 knots and up.
This is because they can turn so much faster, and having fun and playing is what I like, and being easy is great, and that they float in the water, a huge practical benefit when they go down or wind drops.
But in 4-6 knots they simply can not do it anymore, not sufficient apparent wind nor peak power and sits too deep so pinched too much, and I use a high AR foil kite or race foil kite, even with the risk of swimming