Thank you! That was as extensive an answer as one could wish for!
I have found the local importer for Dow and sent them e-mail...
Karel
Hingene (BE)

I don't know what the situation is like in your country, but here in the USA we
don't tell the Dow rep that we are going to use the foam for airplanes. If we
do they won't sell it to us.

I build lots of boat docks and boats G