Hmmm... A maj.

I'm so used to playing bluegrass songs in A that I guess I just assume it's a good key for mando! I find A pretty good for open string drones in solos. Yeah, I like A.

Actually, I'm not keen on the key of F on mandolin, and luckily I rarely, if ever, have to play in it. Maybe on a couple of jazz songs if I sit in with my old band. Other than that, nah.

E maj is a horrible chord on mando and on 'ukulele!