I go with Mooh.

Any guitars the old-time cowboys actually played were pretty much certainly what we would call "parlor" guitars now, since all guitars were that size then.

A 000-something or an OM is a good compromise, though.

I think the ideal cowboy guitar would be one of those real old Gibson small, all-mahogany, round-hole archtops. I don't know what they were called.

Peter.