RedGreen,

Another option for you ...

Heculiner. I just got my cab back from the blaster. I didn't have it epoxy primered so I applied Heculiner directly to the bottom side of the cab. It cost me $59 for 1 gal and thus far I really like it. When I am finished with the body work I am going to give it 2 more coats for sound proofing. It looks very professional when you are done. I can send some pic's if you would like to see it.