I've never had much luck shooting TMax for getting much expansion. I have heard that Ilford films expand much better. (not to get on a tangent...).
Also I will not have access to any Pyro, so I figure I'll do a more 'traditional' developer.
I'd be afraid I'd be biting off more than I can chew tackling the 12x20 *and* Pyro. Whew!