"Are there any regs that state where circuit breakers can be located? I have my hydraulic pump mounted on a bulkhead behind the co-pilot seat and would like to place the main hydraulic pump circuit breaker on the enclosure I've built around the pump."

I know of two flying Legacys with the hydraulic pump circuit breaker mounted exactly as you've described.  (They also have the pump mounted behind the co-pilot's seat.)  I don't think the location was specifically pointed out to the inspectors, but there were no issues raised over the location of the breaker.  I think this location makes a lot of sense as it minimizes the amount of heavy gauge wire required for the pump circuit.

Tom Gourley