I've also used my HPS for vegging, and didn't experience the 'stretch' it supposedly causes (which I was surprised to see) ... the only thing I know about the HPS spectrum, is that it supposedly replicates the late Summer/Fall sun, which is lower in the sky, and filtered thru the atmosphere ... as a photography student, I was taught that the sun's angle, changes its color temperature, etc... dunno if that answered anything, but I have 'happy typing fingers' this morning