My new Trek (Elance 400) has malliard 600 hubs which spin great and seem to work quite well so I have no interest in ditching them. The rear hub is currently set up w/ a 5spd HG freewheel that functions well but on downhills I spin out. Can I put a 6spd HG freewheel on there or is there some sort of hidden issue that I don't know about?

Second question; Can I run 700x 32 tires on a 14mm wide rim or is that pushing it? I think that is it for now. Thanks!