sounds good for now, i'd consider maybe lowering it to 18 inches if possible, dont want them to stretch too bad towards the light, i like to do a few days under cfls before putting under my hps, you can keep the lights closer and reduce stretching to an extent. When they get bigger get them as close as you possibley can, my plants sit about 6-10 inches from the light and are doing great. Just watch for heat, is your light cooltubed? it really helps, w/o it my light puts out way to much heat to get the plants close enough where i like them.