I am considering purchasing some grow bags to supplement my garden space for tomatoes but I am not sure how they work. Can even the largest varieties of indeterminates be grown in them? Do you get the same productivity as you would in the ground? How do you support them adequately? What do you use for soil and isn't it expensive to fill them with soil? Do you do anything to weigh them down? Can they be moved around like pots? Can you recommend any? I was looking at the Gardeners Supply bags, they look about the best but they are 15.00 each plus 15.00 for each cage they show with them. That is 30.00 per plant, although usable for more than 1 year. I would be willing to try maybe 3 at those prices for the first try, but if there are better ones out there I would like to know before buying.