Check out www.reptile-cage-plans.com/

This guy has created the ultimate DIY for EVERY sized enclosure...stackable units (not really app to a burm :-) ), corner units, plexi hinged doors with locking mechanisms...he includes lists for materials needed so there's no guess work. You can build anything you want to your specifications.
I'm going to build a stackable rectangle for my BP...you only pay $27 or so to access all the DIY drafts...you don't need to be an amazing craftman either. It's pretty basic. It also helps you to create your own flexwatt heating elements and install lighting!!