The smallest readily available (2nd hand of course) BCC# is the 12 bass hohner trichord which is very similar to look at to the HOhner Corona & was available in 2 or 3 voice versions with very little difference in weight & none in size. Theo Gibb trading as The BOx Place in Gateshead sometimes has one or two available & will rebuild/tune to customers requirements. The next smallest ,as far as I am aware, is the 48 bass Casali which is tuned 3 voice musette . The bass are 12x4 which gives scope for more keys than the common stradella arrangement of 6x8. I have one of these & would not part with it for any amount of money! The next jump in size is probably to 80 bass.

I have tried a BCC# Benny a few years ago & the treble end was brilliant but it hadd the standard 'melodeon' i.e. push/pull bass which defeated the whole object of having a chromatic box. If there is room for 12 bass yu could have them tuned to the stradella system like most hohner trichords (a few had melodeon bass) Another idea which I understand Fergie MacDonald has on his 2 row is to have major chords only , I don't know which he has but on a 12 bass very small box you could have major chords enough to provide a bit of harmony & rhythm from A flat up to E.

ONe of the big advantages of the BCC# over the BC is that if you learn to play it first as a BC i.e. on 2 rows you can then , using the CC# rows play in the flat keys using the same fingering e.g. BC rows G fingering = A flat on the CC# rows etc etc.

just remembered Serenellini have recently made a small ?60 bass for a Shand Morino player wanting something lighter so may be worth talking to. (I have a serenellini DG salterello which I am very happy with0

hope this is of some help to somebody somewhere
george