Advantech may be the flattest and stiffest panel on the market. I mention predrilling a pilot hole in what I assume is Mianne because I have seen those crossmember frames split with screws.
I mention construction screws because at some point this project will be disassembled and a snapped screw head is a royal pain if there is thought to save the cross member.
I am actually shooting brads over Loctite's Pro Line urethane mostly in module construction and bolting modules together.