"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

Is there a foam that would suit?



Oh... and, I would use the highest-expansion foam available in order that
fine details will be reproduced. Cap off the whole affair with a final
sheet of poly in order to force the expansion back into the cavity.

Regular "great stuff" will work just fine, so long as you lightly spray
the inside of the (lined) cavity with water just before applying the
film. Great Stuff, being a one-part mix, requires moisture to cure.

LLoyd