The 66's, I have, had strips of foam in the rebates either side of the baffle but only in lengths of about 3" to act as padding against the grille cloth stretched against the back of the steel fabricated cover. It didn't look like old adhesive that would have been affixed to the hook part of the velcro - could be wrong it was in a pretty nasty condition but flakes of old foam were there.
The foam on the padded strips was all but eroded and thinned with age but they looked an original fitting. If tolerances are that tight then using a padding strip might be a better solution as the material on the grille covers is pretty thick anyway, you have me wondering about my rebuilt cabs now, still unassembled, I'll have to check on the gaps I have made.
I've seen quite a few pictures of the later 'woodies' with no velcro or pads shown.