I did something similar to that with my ea81. I used high quality spray foam for insolation for filler as my foam had cracked pretty badly, and then used some fiber glass over that and a small amount of bondo to smooth it. The problem with this is the old vinyl is very brittle. My dash has re-cracked right next to the areas I repaired last year due to the vinyl shrinking away from the fiber glass. I think in order to keep it from cracking the old vinyl would have to be removed completely. Maybe the method used above would work better with plastic welding, but I'm not convinced that it would. I will say the flocking I used looks, and functions great!