wow, it has been a long time since my last visit to the rc subs forum... anyways, i think with thick balsa, and some fiberglass covering, you probly wont need to worry about it being light. that should be fine. first, you will want to figure out the size, and if it will be dry-hull or with a watertight cylinder. it looks like you will want a dry-hull, as you will have wood on the inside. this will complicate the building of the hull, but then its alot easier to put the electronics in. i am most likely repeting stuff you already know though.

benthehen