I'm only doing my first grow, so don't consider me an expert. I'll just tell you what i've seen in the last 1 and 1/2 months.

I'm growing ICE, Jock Horror, White Widow, and Bubbalicious. (I really recommend Female Seeds. All the seeds of each pack type will germinate and grow with the same characteristics, whether that be bushiness or stretching. Whereas the pack of nirvana seeds I got, showed characteristics that seemed as if each seed from the same pack was a different type.)

My ICE, Jock Horror, and Bubbalicious, of which i have only one of each when comparied to the white widow seem to be stretching. But I have the clfs 4 to six inches from their tops.

IMHO, some strains, maybe sativa domininant strains (speculative), tend to stretch regardless of how well you light them up.

My white widows, of which I have 7, are short and busy. In fact my 4 day old ICE plant is taller than 4 of my 2 and 1/2 week white widows.

I see posts, here where people put their pics up of a plants that only have 2 sets of true leaves showing, and if there's a lot of stem showing. Every tom dick and hairy will put a response up saying: "hey your plants are stretched...lower your lights.

From what I've seen, stretching is bad if you keep you lights too high, but the fact is, at least from the plants i've grown, some plants will stretch no matter what type of light strength you give them.

As for the HPS, I'm doing the growing under a 600 watt HPS (horitlux), and the light is about 2 and 1/2 feet above the tallest plant. I'm using the HPS to grow just at the start of my noob hydro grow because I set up the cab and it was just sitting there while my 2 125 watt closet just didn't have anymore room for plants. Anyway, some of my white widows are only 3 inches tall but are so bushy even with 5 sets of leaves already.

My Ice plant is only a few days old and is almost as tall and my white widows, but only the first set of true leaves.

I gotta tell you though, theres a lot of expert advise here about growing under HPS and how CLFs or MHs are better for grow, and maybe MHs are better. I don't know, i've never used one. But I can tell you that my plants under the 600watt hortilux hps are growing about 70% faster than the ones under the 125 watt clfs, and I only have 2 plants under each 125 watt clf, so their being enindated with clf light.

These are the results i've seen with the equipment i've used. So take my info with a grain of salt.

One off topic note: I also have 2 potted plants in a soiless mix of 50/50 perlite/peat moss. And these guys are launching like rockets. I've never seen plants grow so fast, and I don't have to water/feed them but once every 2 weeks. The seems perlite keeps the entire pot moist but not damp.