I get an itchy "add to shopping cart" trigger whenever I see those, look very useful. Plenty of shop-brewed designs I looked at with custom corner brackets, so I've still not pulled that trigger for the pre-made versions.
The tie-down strap idea looks good, but I never had the heart to cannibalize one of my "precious's" since I'm down to maybe 20 or so. Good call on the reprofiling since those corners will bite into anything you find dear on the project.
Might be time to fire up the ponder engine and see what's what.