Got my iron from Edcor, time for a trial fit. Tomorrow I'll be drilling and punching, and rolling the dents out of one of the transformers. I'm liking the layout in the first two pics. The 12ga chassis will hold all this weight quite well.
Shannon, these transformers are the same size / weight as the CXSE25's tour using on the 300B amp so the 3mm plate should be more than enough.