ORIGINAL: WEDJ
"supposedly" the grooves help in knife-edge flight.
Personal opinion - it would be hard to measure the difference
Joe Bridi did the same on one of his canopies. (Super Kaos, UFO?)
I have heard that, too. That's why I asked about it before just removing them. On the glass fuses it also adds some stiffness, but for wood I think it won't matter. Especially to my duffer thumbs; a world champ I am definitely not. And I think I can do more damage by not getting the grooves even on both sides than any help they would offer. Slab sides it is!
The UFO and Dirty Birdy canopies had a waisted groove near the bottom as you mention.
Thanks,
Mark