Dang, I LOVE that. It warrants a song...Blackbursted the edges, top, and back today, with a few more clearcoats.
This is 90% hollow and weighs about a pound.
It has a neckblock, tailblock, and a bridgeblock to support a TOM and tailpiece, which you can see through the rear cavity shot.
It has a central connecting 'beam' that connects those three, which you can see through the bridge pickup cavity too.