Two bits....

[iiipopes]

If I remember correctly, the venerable Thompson version has sliding levers, like a real bench vise has, so mouthpiece diameter is not an issue.

[imperialbari]

Supplier for the brass & music industry:

[TUbajohn20J]

On the old fiberglass King sousaphone in 6th grade I used 2 bits. On the Conn 22K in 7th and 8th grade I used 1 bit. On the Conn 32K in high school I used 3 and sometimes 4 bits because the mouthpipe was so low it needed that many just to get the mouthpiece up to my chin. On the Conn 20K in college I used 2 bits. And on my Conn 40K I used to use 1 bit but now I have adjusted to 2 bits and have them angled coming in from the left side...very comfortable for me. It really bothers me how most people (mainly students) hold their sousaphones. I'm one out of 2 people in my entire college sousa section that prefers the "Front to back" position, while the others want that "side to side" position with the bell directly in front of their head..almost touching their forehead.. I hate that!!
I've always liked my bell pointing slightly upwards and to the left

[TUbajohn20J]

I agree it's important for a section to match. There's over 20 sousa players here and most of them hold their horns the same way... the "WRONG" way. From far away everything pretty much matches, and really only other tuba players would notice if someone is holding their horn different. I've always held my horn like that..more comfortable.