My space is 2' x 3' so yours is just a little bit bigger (.25'). My space is crowded with 3 girls. I can't imagine trying to cram 20 or even 9 plants in there. Sour Crack would be a good choice for a SOG as they are fairly short but they tend to be on the bushy side. My current SC at 40 days is 13.5" tall but has a 18"D. You got to give them a little room to spread out. You could probably fit 6 or even 9 of the 2gal bags in there but your per plant yield will probably suffer. Your total yield would probably be just as good doing 4 plants. If you really want to do lots of small plants, go with even smaller pots. Check out grows by
@Spanglish, he did grows in 1liter and 3liter pots (I think). He was growing in a cardboard box 2 plants at a time with some nice results.