In our boat, either Sabre or the dealer separately routed the outputs from the rule pump and the manual aft. They then joined them in a "T" about 12" from the overboard discharge. Works beautifully. Note that I discarded the check valve that someone put on the rule pump and installed a vented loop to minimize backflow.
To be honest, if I'm ever in a situation where I need both pumps to keep the boat afloat, I'm breaking out the bucket and switching the engine intake to bilge intake!
Sabre 38 "Victoria"