This is the whole reason why MH is the "Classic" veg light. And why "Mixed Spectrum" or "Ceramic Metal Halide" bulbs offer "The best of both worlds".400w MH lamp for vegging right now, and noticed they dont grow up... they grow out....
Used a HPS and they started to stretch up, went back to MH, they stopped growing up and started getting wide again.
Does anyone specifically use MH to save space?