I see Pedaltrain II (PT-2) pics here, some with a voodoo labs pedal power II mounted underneath, some on top. Do the pedal power units mount easily underneath or is a special mount etc required?
The newer Pedaltrains actually come with the mounting brackets. It's a simple process, really just drill four holes, and attach the mounting brackets, then screw it in place and you're set.
However if your PT2 did not come with the brackets, as it was probably an older model, like the PT Pro I got, you can email them to order just the brackets for USD$15 shipped. That's what I did