As for the flat 1/2 step tuning; the only really good reason for this - and it's a good reason, is a balls-on B natural. Low B will be sharp in this configuration, but low Bs are damn rare in Euph music and C is fine; but a flat whole step means you still have a sharp B on the staff.
When I got mine, it had a flat 1/2 step and sleaves added from a bass trombone for a flat whole step too. Not a bad option (like the Eb/D option on a lot of bass bones). Build 'em in +1/2 with the sleaves for an extra $50.
J.c.S.








