Just a heads up for those planning a Crown-Tube swap with TC's or Gen/Clarks equiv.
The BP case is drilled and tapped to accept an M3 X.35 Pitch tube. The TC tube and the Aftermarket Gen tubes are M3 X .3. While this might not sound like a big difference, it is actually a "no-go" without the proper threads. I contacted CaskerCo about this because Otto, Casker, Esslingler all sell a .35 pitch tap, which will not work with their .3 ptich tubes. .35 is an IFI standard size which explains why they all carry them. Esslinger probably thought I was nuts and replied that they can get the .3 pitch if "I" wanted them too. lol, I bought tubes from all of them. They are all .3 pitch. So they can do what they need to do but..me.. I vote for the proper threads in the case.
Don't believe me? Buy a thread pitch gauge and see for yourself.
I re-tapped the case to .3 from a .35, it's not ideal but it holds extremely well if you do this correctly. The TC and the Gen tubes are longer than the rep anyway, so you have twice the thread engagement into the case.