Beatle would be the man to talk with about getting the latest specs. However I still don't believe there are any better authorities on tank bustin' than my crew. My XO Edwin was the high killer with 17 in DD'05, myself with 15 and my son tied the top German AT'r with 13. We were and still are the only AT group to ever stop Bill Bailey and his tank corp.... not just once but twice.
As for construction materials I recommend ABS rather than PVC, it's much lighter. I've even heard of guys using "Pringles" canisters for an ultra-lite body. But I like ASB best, it's light and takes abuse. You might also want to look into building a PIAT or M1A1, they're the smallest & lighest Allied launchers.