If you're patient and have a vast assortment of Philips screwdrivers so you can find one that fits the little screws that hold the individual butterfly valves in place, you can remove the plenum, then the screws, one by one. Then Loc-Tite 'em in place.

If anyone wants the dimensions of the bushings used for the pivot arm, I've got them, measured down to the 1,000th or 10,000th, can't remember which, laying around here somewhere, in case you want to have some made. I had a one-off set made out of some unobtanium that a guy who makes parts for NASA made with my brother's help.

John B.