[DonRotolo]

Thank you Rich. Our design has the 'lower' frame (at wheel level) just a bit smaller than the 'upper' (bumper zone) frame, about 1/2" on all sides. The upper frame is just under 27" wide.

The simple solution is not adding dummy fasteners, but a 1/4 (or 3/8", whatever) strip along the outside of the frame perimeter. Nothing says it can't be birch plywood (lightweight) strips.

In theory, the lower frame could be as much as three inches smaller, eh?