I'm going to fire up this topic again... For the last couple of months I have been using my PCG at the front of my chain, typical settings (99% of the time) volume 3 oclock, comp 10 oclock, nat 9 oclock. For fun, I moved it to the end of my chain and have been pushing the volume up to near max with the other settings remaining the same. It just kills in both positions (front and back of chain). I really like it with the volume pushed particularly when I'm playing in a band setting. The thing that I love so much about the volume boost from the PGC is that it doesn't add any dirt to the overall tone just, as BobbyD would say, "sweetness."
I have also found that it can do some very subtle and pleasing eq correction when used at the back of the chain. I have a Cornish P2 which some find to be a little dark, the PGC works very well for correcting this while still maintaining the integrity of the oh so sweet fuzz tone of this pedal or anything else that's in front of it.
I know it's a little corny, but I really could see where you could have a PGC at both ends of your chain.