Rich, I think I'd really enjoy making a few different ultralight cabs using alternative construction materials and methods sometime. Sounds like a fun little project and challenge to see how light a cab could be made and maintain it's sonic integrity. I'd be most interested in testing materials and methods out on a Tuba or Titan design though.
I'm going to try to keep this current (DR200) build as close to the plans as possible and just use thinner ply and remove excess material/weight throughout the build to achieve the lowest weight (reasonably) possible.
I keep using the word "reasonably". Reason is, I'm not aiming at a "no holds barred", light at any cost, build. Reasonable convenience and ease of use will take precedence over weight reduction. I want the same usability and function as I'd have if I built them by-the-book, but as light as possible within that context.
Wish we all lived a little closer to each other. Would be a fun little group project to build with some of those panels you have