Progress update...
Step 1: make a newspaper template
Step 2: transfer template to 3/4 in. foam board, bevel the edges, kerf the back side to make it easier to bend
Step 3: fashion the behind-the-scenes supporting/foundation piece, made from a 2 in. thick piece of foam. The bottom of this part is also shaped because the grille opening is "dished" from side to side. Secured with two screws through the bumper cover at the rear.
Step 4: et, voila!
Still lots of finishing work to do (e.g. like making a finger hole so I can reach the hood release lever
), but that's the big stuff completed. At least for the upper block.