The reason I have chosen to go with foam is price, 65cents a strip for foam or $3.45 a strip of cork. We get ripped off in Australia and to import the cork would have cost me a fortune. Saying that if there is anybody that lives in OZ that know where to get cork for a reasonable price pls pm me. I have agree about the quality of the foam. I bought a box and it does vary alot from piece to piece, some thick some thin and even I have had some with sides missing.
The subroadbed is particle board covered with a layer of 3mm mdf. I will be painting the whole surface hopefully this week. As for moisture, the layout will hopefully live inside soon HOPEFULLY. Also I have added alot more risers than I needed to prevent any sagging.
Track and roadbed is a bad place to compromise in N scale. Just my $0.02. Good move to seal the mdf, have worked on a couple of layouts using 1/2" mdf and it was very solid and stable.
Cheers, Coxy