I did something similar to Dru on my CMC, and made the shields out of HVAC galvanized sheetmetal from a Heating/HVAC place. Maybe $20 bucks worth of metal (actually, they gave it to me).
I have two pieces, one a giant horse shoe attached from the bottom, going around the back of the engine and along the sides to the firewall where it attaches to the firewall via a rubber sheet that looks suspiciously like a rubber stair tread. All that just screws into the CMC body frame with 10-32 screws around the engine and seals against the engine tin with Frost King door weatherstrip from Home Depot. I do not need the "H" gasket from a beetle or bus - there are no gaps.
The second shield attaches to the top of that body frame and goes across the back of the engine compartment (near the tail lights), but it has a kip-up at each end to seal against the body just beyond the tail lights where there's a big hole.
I have paper templates of them both, marked with bends and approximate hole locations. I can send them for the cost of packaging and postage - $5 bucks and they're yours, just PM me and we'll chat.