Buffermount will absolutely work on large prints. I've never once had an adhesion issue with it. If you're concerned about it adhering as it cools I would say two things: Quite a bit of adhesion occures in the press, and you'd be hard press to lift a print off of it straight out of the press; Secondly, if you did have a problem, or wanted to prevent any potential problems then all you need is a clean sheet of glass to weight the print with as it cools.
BTW, there is also this new(ish) product called Artcare Restore that is an acid free foamboard with an "archival" heat activated heat releasing adhesive. It's a little finicky, but you dry mount at a fairly low temp, for a fairly short time. It's the slide film of drymounting: It get's more adhesive as it's heated till a point than it get's less adhesive. So you press it within a certain window and it sticks, then to remove it you heat it again. It's not perfect, and with heavy fiber prints you pretty much have to weight them with glass after pressing, but if you want a nice presentation but don't want a permanant bond, than I would suggest this. Might be hard to get for some people, ask a frame shop. It may only come in 32X40" sheets too, by the box, I'm not sure. Buffermount is also removable, but have you ever done it? It sucks, and it's easy to damage the print in the process. Not something to plan on doing.
Color mount is not remotely archival, BTW