Hard to say....in full sun with a smooth grow, i expect autos to grow close to the sizes of the breeders specs. For large size autos i would give 3 foot diameter holes. If your NL is supposed to be a standard size auto 2.5feet will be enough space. Beanpole or small autos you could get away with 2 foot holes(even 1.5 on the smallest)
Honestly if you are worried about air hassles, I wouldnt worry, especially if you get a jump on the season under lights....a may the 1st start under lights for the first 30 days and a june the first plant out will have most finished up by mid july(long before Johnny Lawboner is eye spying in choppers)
Win,Win!!
Be careful of high midsummer relative humidity though!! It can turn some strains to moldy messes just as easily as ample rain can!
Go get 'em bud, autoultimate