FWIW - After reading all advice, I tried my trust handheld jigsaw, a nice powerful one, and it was a piece of cake. Marked lines on asphalt, lay on table foam down with edge to be cut just off table edge. If it was bending I held it up all level so foam cut would be even. Absolutely no mess and takes 10 minutes. Experimented with board on top to compress foam while cutting - perhaps neater, but a PIA so I didn't do it that way.
Now, do I REALLY need to solder those connections?