You can use one switch to control LU and OD if you put a NOs switch on the ground wire for lock up and adjust the spring tension on the switch to lock up above your OD shift.(say 50 MPH)

http://www.summitracing.com/parts/NOS-15660NOS/






The nitrous oxide fuel switch is infinitely adjustable thru the allen threaded plug on the end and even different springs. I can tell you that a little bit of turn on the plug makes a BIG difference in the shift point.