I had mine mounted on the rail low for a while.
as said before, if the tank ran low, it would fall over.
the other issue was, the guy that ran my exhaust put it really close to the pump.
no issues normally, but we went to see christmas lights one year and it was stop and go traffic for over an hour or two. the pump overheated and wouldn't put out enough pressure and my car stalled in the line up of cars. was lucky and there was a place to push it out of the traffic.
couldn't figure it out, but sitting there it cooled enough to get it running again, and I flew out of there to get it home, since I didn't know what it was.
finally figured it out after a bit of trouble shooting, and decided to move it and do the surge tank at the same time.