Wayne - My "on the bumper" was only a 175 shot.
I didn't read through this and know he was asking to do it first pass. As said before - first time out with 300 is just asking for trouble. I've done this and been successful and I've done this on another setup and got hurt. I do NOT take that approach anymore. Ask yourself, what will I gain vs. lose by spraying that much first pass?
The only way that I approach new setups now is baby steps. You'd be amazed to find out how many times myself and others make partial passes to dial in a car. Tons. Seriously.
BTW - my setup = 29.5" tire, 4.00 gear and 4000 Neal Chance converter