MH light distance for 600w veg

Oh boy, yeah i remember that it's much hotter than a hps lol.  The leaves curling it's the plants trying to keep the water in itself because the evaporation is too important. Interestingly, the other side is when the medium is too hot. For your question, 1m, maybe 1m20 or more. I successfully cloned a few times under 600w hps so why not sleedling with a mh. If you can dim it to the minimum, i think 60/70cm should be fine until they grow a few pairs of leaves. Temps will tell you anyway!