These are great responses! This shows what a rookie I am. Seems like a lot of people share your low opinion of cork. I just thought it would be an easy material to work with, but it isn't looking that way.
Buddy, thanks for the extensive, informative response.
Namekagon: I like the idea of trying the basswood. I'll give it a shot!
Coachbob: I did a quick readthrough of your article, and it looks terrific! Thanks for that, along with your recommendations in this thread!
RHenn: what sort of foam were you working with?
Great tips! Keep 'em coming!
Hugh