The tympan framework is done and I built the frisket frame in exactly the same fashion, just a bit smaller so it nestles inside. Here are some pictures showing what tympan frame looks like, along with some details of the corners.
Here's the entire thing, upside down.
Here's a corner, from the bottom. The CF cloth makes it a little rippled on this side, but the other side (where it's glued) is quite smooth. Hmmm, that's wrong. I should have put glue on the rippled side and left the smooth side up.
And here's what it looks like from the top.
The bars are 1/8" thick and the L brackets are 1/8" thick, so the corners will fit between the cylinder and the 5/8" furniture.