snap down = ng for trailering
I usually do a ratcheting belly band with multiple tie downs either to trailer or under hull side-to-side.
Fabric doubled at hard pints (cleats, tm, aft corners, etc...)
As many tent poles as necessary; also re-enforced.
Use heavier material; Sunbrella+, or at leas 11.5oz/yd ...pvc18 (or the like) is BOMBPROOF (but make for a heavy cover)
I'm a marine canvas fabricator