Block sanding hood

[72bowtiestepper]

I finished stripping the hood on my 72 C-10, and want to know the best method of block sanding it after shooting the epoxy primer then 2K primer. I fixed a few small dents, but when sanding the flat centers of each side of the hood, they tend to "push in" with any pressure. The hood supports on the underside of the hood do have the foam material intact, but the metal "gives" up top with sanding pressure. Thanks in advance for any ideas !