A long time ago, he was playing one of our local dances and he asked me to sit in for a couple songs.
The accordion was in Ab, and it might be the same one. I remember my thumb was swimming in the thumb strap - I have big hands, but I guess not as big as his.
I have an A box, so, should work. I have a similar vocal range as geno, so when he does something to dodge a high note, I usually can't hit it either. In Jeunes files DE LA campagne, he misprounces campagne (compawn) because that allows him to hit it. I just do it in D on my GC box.