Christian,
Thanks for your reply.
Yes I'll play Cajun music, but tuning a one-row accordion in just 3rds and 5ths (and sometimes high 4ths) is suitable for any kind of music IMO, as long as you don't play along with other 12TET tuned instruments. My question was specifically about the tuning of A and F.

I just checked Lepistö out, seems to be a great musician, thanks for the tip.

Regards,
Jonas