One suggestion. Have you thought about grounding your RPM relay through the inertia switch? That way you restore a critical safety feature but don't have much of a load going through that switch as well. Basically if you are in an accident, the inertia switch trips and kills ground to the RPM relay. The relay should then shutoff and kill power to the pump.

I don't have my schematic in front of me, but you might even be able to utilize the old fuel pump wiring. Connect the two old pump leads together so now the wire running back to the RPM relay is grounded via the inertia switch. Reconnect the wire to the RPM relay but on the ground terminal instead. This is assuming nothing else is connected to the pump power lead which I can't verify at this moment.