I want them to reach full potential so I'll wait. They are growing very fast, the larger 2 about 40 inches and the smaller 2 about 30 inches, I'm glad they are evening out to one size. Four feet high would be the limit as I've got about 8.5 feet to the light from the container. Today is day 21and I keep raising the lights. Despite Ed Rosenthal's book saying maxing out co2 and temp to 85 degrees is optimal, I'm finding if I keep it below 80 degrees, floating between 75 and 80 per a.c. cycle, the leaves no loner slightly curl inward and now look perfect. bman707