for anyone interested in a little more detail, here is how i got the stamped floor ribs to nest better in the over-lap joint.
1) slice along the outside of the "spooning" rib. close to it, but up in the flat of the panel.
2) with a flat dolly of some kind, use a ball peen to hammer the rib out wider.
3) now that the panels fit snug, tack weld the seam from both sides. more hammer might be needed to perfect the fit.
4) seam seal everything in.