Well. my experience is rather limited with curved vanes, but, compared to conventional vanes, Spinwings appear to be rather fragile and prone to damage. If there were contact, even very slight, I believe it would leave a recognizable mark on the vanes. Perhaps the difference is weight; more weight at the back of the shaft stiffens the arrow. Do you have a way to measure the weight of 3 Kurly Vanes, plus associated paraphernalia (tapes, etc.) and compare it to a similar set for Spinwings? I have weighed a Spinwing set and came up with something like 5-6 grains, much less than any other type of vane, but I had no other type of curved vane acessible to me...the closest were natural feathers, 3", and even then they were slightly heavier, as I recall...
So, if Kurly Vanes are heavier by any appreciable amount, that could explain the difference in behavior. Not better nor worse, merely more suited to your setup.
YMMV, etc.
DF