From the people I know and myself when I used Nitrous you jet the carb for motor and leave it alone....your Nitrous Tune-up is completely seperate. Start out with the recommended jets and sneak up on leaning out the fuel jet and the fuel pressure. VERY small steps and read those plugs!!! JMO
As far as Activation I have always used a WOT switch on the carb.
A safer way to go and 1 less step to do while trying to make a pass.