Make sure you have a lot of fuel cell breathing with a good roll-over vent line, as big or bigger than your feed line. You cannot ever have any negative pressure in your cell or it will stop flowing. It is even worse with a belt drive pump.
I agree with Joe, sell the piston pump and install a good diaphram pump... it will do everything you will ever need. I have run a good diaphram pump with as small as -8 (1/2") feed line from the cell to a 650hp methanol dirt modified big motor, and a regulated -6 (3/8") bypass return line back to the cell, and never had a problem with enough fuel flow. I have seen numerous times a vaccuum lock on poorly vented fuel cells.
The piston pump is just another gimmick that just does not work for most applications... JMHO... Jim