Most everything I've read, about derimming, says that the excess silicon you see gooped in the corners there is not necessary. All of the structure and (most importantly) the seal comes from the thin bead between the panes. I don't think it would be an issue if you carved out some of it, or thinned it down a bit. Nice job btw derimming that. Exacto knife sounds like the way to go, huh? I tried to do the same with my practice 20L and chipped a bit of the edge... then gave up. Good job... I'll keep watching your journal.