Right-Angle Draw Latch

Even though my hatch is as simple as it can be, a single piece of 3/4" plywood, waterproofed with three coats of poly mix and two coats of enamel on the inside, three outside...it is starting to get a little twist in it...from being raised and propped open for months at a time (I should latch it shut when not "working on it"!). If it was to be secured, it might've done the same twist anyhow, I don't know. Well, anyhow, whereas it once sealed perfectly all around, it is now not sealing at the bottom (the rest of the perimeter seals are fine). Until today, that is. I screwed a round tube seal (from a household door seal kit) to the bottom-lower inside edge of the hatch, and mounted a set of adjustable right-angle (corner) draw latches to pull the hatch tightly against the trailer.some deformation, after all, the hatch is 49"x48", with no inner bracing (really didn't want more weight at the hindmost part of the trailer).
I used scrap aluminum flat stock (leftover from other trailer projects) to align/shim, and tension the latch springs to bring the hatch fully up against the seal. If the hatch flattens out again, I can remove the shims...if it twists more, I can add more shims (and a thicker seal. I should've anticipated