From the reviews, this design seems to fail at the upper bent end so I'd much rather find a platform with better mounting points like the one on Cracker Larry’s No Excuse build:

I've also considered a simple step like the Perko with a good, sturdy grab bar mounted within reach on the rear deck.
What have other people done? Am I worrying too much about the bent ends or do they work just fine? Does anyone have a recommendation for a platform with well-designed mount points?