Actually the spindle thingy, if I am visualizing what you are describing, is more commonly known across different SPG manufacturers as a High Pressure Restrictor. Small thin hollow rod with o-rings at both ends, some manufacturers have a disc in the middle of the tube, making it look sort of like a top, some have only a tube with washers. You definatly need to install the rod and make sure that it has the washers on both ends.
Going from the description from my toolmaker's I get my regulator tools from, "The restrictor is used to seal the HP hose to a submersible pressure gauge, instrument console, or computer."
Going from the description from my toolmaker's I get my regulator tools from, "The restrictor is used to seal the HP hose to a submersible pressure gauge, instrument console, or computer."