I have shortened many Silca pumps sucessfully. Using a tubing cutter, cut the bottom end off the plastic pump, not the top. Pick or grind away the bottom insert to the pump and epoxy it back in place. Use the tubing cutter to cut the aluminum shaft to the handle and re-insert the nut in the end using a pin-punch and hammer to set in place. There are a lot of long Silca pumps out there very cheap. Size doesn't matter after all.
Ted Trambley
Martinez,CA USA