It should be sweet!
Are you looking for an OM 4-way? I should have one for sale in a little bit...
Isn't 2" plumbing a big pain in the butt?
You may find your overflow boxes will be huge to accomodate the 2" plumbing and the 1.5" plumbing, especially with only 20" depth to work on. The boxes should take up a good chunk of each side.