Sounds good man, thats a big crop for a first up ! I'm an outdoor dude, my philosophy on growing is to keep as close to nature as possible. I'd be doing bigger holes if I was you, 2 Gal, 7.5 L, not much man. Yes they'll grow through to the natural soil but if the soils crap underneath your mix, it WILL cost you in yield. It's all about the soil man, give them plenty to grow into. I grow in organic compost and mix in an organic fertilizer which contains chicken shit, fish meal, blood & bone, seaweed, worm castings , rock minerals, natural gypsum, sulphate of potash & rock phosphate. I also mix in perlite & vermiculite and course river sand. For photo plants I dig holes about 4ft deep & 3ft wide and load it with the mix. I will be growing my auto's in 80-100L pots with the same mix, would advise you to dig holes about that big for your auto's (approx 20-25 gallons). I will probably get crucified for saying this is over the top, but in my experience with photo's it was well worth the extra digging and as auto's are a different beast, any stunting will cost you dearly. Good luck man