ive always heard you should never hit the N2O until your at 3k RPM so once im in 2nd gear and around 3k i usually hit it....but i have used it out of the whole with no difficulty's.
I have a MadZ28 tune with the timing acutally advanced..like i said the only other thing i did was run colder plugs, i dont think we would really have to do a whole lot to run the N2o unless your looking into getting the safest set up you can get.

 

im at 188000 miles and i still hit it with the 150 hit. it loves it ha ha not pulling a bit of timing either

 

I'm spraying 150 shot

 

I'll be spraying 125-150 on mine, the motor isn't my concern, the trans is. I have seen so many people spray the living **** out of LT1s it's sick. Most broke transmissions well before motors.