Chris,
Question, Everything I have ever read on Yota frames is, If your gonna weld somthing like a link mount or a spring hanger or somesort, that you should plate the inside of the frame in the area that you are mounting to as the metal is weak and will rip.
I dont know where the pic is but there is one on P4x4 that shows where some guy mounted a link on the inner frame and it ripped a big ass hole in the frame.
Is that what the longer angled pieces are for is to distribute the stresses over a larger area??