instrument bezel repair question

JBWeld for the missing chunks. I duct tape wax paper to the back of the panel with some sort of stiff backer like popsicle sticks or heavy cardboard, then fill in the gaps and sculpt to the rough shape. After curing, peel off the tape/backer and finish shaping the patch.
For the screw holes, just epoxy small flat washers to the back side of the panel- the thickness of the panel gives the screw heads a recess to sit in.