Fastbuds Perpetual Harvest

You'd burn the shit out of them with a 1000 watt hps. Autos' light period is longer than photoperiods so you have to be careful with your DLI if not supplementing with CO2. At a guess you would only need a 400/500watt hps in that space . So be careful not to overdo it. Also Fastbuds recommend the max pot size is 20 litres for autos. As they only really veg for 35 to 40 days. So there is limited time for it to establish a bigger root mass in a larger pot.

I am using 5 gallons(19 litres) fabric pots.

1 gallon per month / 1 gallon per foot of height... general suggestions. you can get away with less in soilless with chelated hydro nutes (not soil nutes) if doing any 'special' irrigation method like multiple fertigations per day, you need to think about it differently. some familiarity will be needed to know how big your plants tend to get and how quickly they can drink