Me too. Except I use five gal plastic kitchen garbage "cans". Same reason, tho--round containers take up too much space. Square or rectangular footprints dont waste ANY space because you can set them right beside each other.
If I used five gal round buckets, two is all I can REALLY fit under my 600w. HPS. But with the rectangular garbage containers, I can get 4.
I mean, OK, you can squeeze 4 buckets in, but the outside edges of all four plants dont get under the light. Make sense?
In a five gal you can easily grow a plant that finishes at 4-5 feet tall.
I start mine in 12 oz. Solo cups from Walmart then move them to the big container when they're 8-10 inches tall.
BTW, I grow Hempy style.
CW