It took a little measuring, but they fit fine. Not sure how this will change the pitch, other than lowering it just a bit. If you notice, it's lacking bell screws and flanges, as well as a brace. The reasons being that I have no bell screws on any of the Barcone sousaphones (I have no idea why - they're all missing them) and I don't have a way to make a removable brace for the bell.
Next on the plate, is either going to be the F contrabass trumpet or the start of a single CC Bass Horn. Both will be using smaller bore valve sections than are featured on other examples, and will both take a bass trombone size mouthpiece. One of the tuba players in the community band here in town has agreed to play-test the F contrabass trumpet (he plays a nice Yamaha 822 F tuba), so I will at least be able to get some better feedback on tuning and functionality. The idea is to use a contrabass trombone bell section with a smaller bore piston valve section, though I'll play around with the parts I have on hand until I hear back from Wessex Tubas about how much that bell is going to cost me. Yes, you read that right, I'm buying a Chinese-copy of contrabass trombone. It's cheaper than what I can get from Kanstul or Miraphone or Thein or Rath and will be just as good on what I'm making - prototypes.
The owner of the Eb contrabass flugelhorn is quite happy with his instrument. He sent some pictures of it at TubaChristmas, though most people thought it was just another marching baritone.
Now that the weather is warming up, I'll be able to once again post more frequently on the progress of various instruments.
I started the other day tearing down a rotary euphonium for the valve section - got it for cheap! I even have a lead on another one for just a little more than what I paid for this one.
Also, I picked up a Buescher Eb helicon with a tiny 15" bell which will serve as the body/bell for the new CC Bass Horn. The whole instrument is pretty small and easily fits my design. There's another Buescher Eb with a slightly larger bell (17") that I'm hoping to trade or buy, but need to work out the details. This will, if I can get it at all, replace the larger Barcone sousaphone body I have for the FF/BBb contrabass double horn. Yes, a true contrabass double horn in FF (24-25 feet) and BBb (18 feet). I think the Buescher body is the right proportion for such an instrument and certainly conical enough as is. Although there are a few more details to work out - EXPENSIVE double valve section!