I recently put an 10PSI RPV in the brake line coming off the master cyl, going into the brake light valve/ switch due to complications on using a disc/ drum master on a drum/drum system ( front brakes ither didn't work or came on after rears ), and my brake light was on, probably because of this, and it is still on, I know how the switch works, with the preassure needing to be equal otherwise the side with more preassure will overcome the side with less preassure forcing the ramp on the switch prod, closing the circut. How do I center the switch?