As a sort of addition to the discussion, I do find myself playing with melodeon players quite often - in fact I will be playing over the weekend with Bill McKinnon in Wallingford, (where the Bunkfest was) at his 50th!!
I play an Avalon Legacy L10 which is Mahogany B/S and cedar top, but it is a Jumbo and cuts through rather well but I do use a thumbpick and use 12-56 gauge strings (Elixir).
To be honest I'd always go for a large bodied guitar for that sort of job and at least a jumbo, because of the deep waist, sits down on the knee very well and is very comfy to hold and play and I'm only 5'5"!!
Dave Bennett

http://www.myspace.com/davenbrenda