yes, although i've never done it myself, i've read numerous times that plants that receive both mh and hps light are usually the ones that do the best out of entire grows.... like i've read where they have an hps covering x plants, and and mh plants covering y plants, but the plants that fell more in the middle, the x and y plants, all did the best.. i'm dying to run a test myself, but as of now, don't have the room to do so.. mh's have more uv light that hps lack, and hps tend to have more red light, which is better for flowering, so the combo of both is great for plants from all i've read..