My 6.4 slingwing was on order when my mate said "here try out my 6.4" on his board coupled with a razor sharp moses rear wing...
I use slingshot foils with less sharp wing edges.
30 seconds into the walk to launch, the wind flips the 6.4 straight onto the rear wing, walked straight back with a really red face and something that sounded like hucking fell

I didn't even get to foil it, grrrr!
I gave him the new 6.4 when it arrived and I patched up the 6.4 that I tore, I used white kite tape and local sail maker Z stitched it for $20.