on a single pipe ski that feeds water thru the pipe then into the cylinders,putting a smaller brass fitting inside the dome cover would in effect slow down the volume of water passing thru the pipe and cylinders.on a triple pipe ski the water fed into the cylinders comes directly from the pump and is passed thru a .025 brass fitting to each cylinder,so anything that size or larger used at the domes wouldn't affect the volume of water passing thru.