The relay could interrupt the field cir instead and the alt will cut out.
You could even wire a switch to cut out the alt while on a run ASSUMING your battery can provide enough power for all your needs while on a run. gain a few HP?
Ooo this looks like it could work. Could you please describe the wires for this relay as I don't fully understand how to hook it up.
What would be the "activator" wire? Probably just any wire that connected to ignition considering I could wire it so when I disconnect the master switch it would engage the relay and then what field wire would I be "engaging/disengaging"? The blue or the green on the alternator?