I have been powering my crybaby through a PSM-5 without problems. At the same time there was 4 other pedals on the chain.
I prefer to use the PSM-5 in front of the amp rather than through the loop. It depends on what pedals you are using in the PSM-5's loop. Booster pedals and wah's are usually placed in front of the amps driver step.
What pedals do I own?
I have around 40
Boss pedals (it's a disease) and a handful of others. I normally put 6 pedals in a BCB-6 pedalboard. The distortion pedals gets exchanged now and then as I never seem to find what I'm looking for. The other pedals have been in there for quite some time now. Right now it looks like this:
DM-2 PQ-3B DF-2 SD-1 CS-3 NS-2
There is also an LS-2 on the back of the loop that I use to change amps.
old pic of the whole setup here:
http://www.bossarea.com/test/rig.jpg