I would be growing one maybe two autos under a single mars hydro ts 600 (100w actual power draw) so I don't think heat will ever be an issue. I also would be using passive intake and no filter and minimum/zero ducting attached to the fan so just hanging it in the 4 inch pocket up top and securing it....bootleg grow tbh
So you personally need a minimum of 30cfm but you opted for a 420cfm but turn it down? Ok.
Ok I was just cautious that too much power would not give the plants time to process any air because it was moving through the tent too fast. Hopefully this cheapo pwm controller can reliably half the power and I'll be happy as Larry.
Good stuff, it should be fine the more air running around with fans and intake outtake is best because they are wind pollinated plants, I think it helps them thrive with tons of air moving constantly