mh is used for veging. the hps is used for flowering. you will have to have some good venting to use 2 lights in that space. if you can aford it get a switchable. then all you have to do is change the bulb. do a temp test befor you put any plants in there to make sure it don't get too hot. you don't want to cook your plants. chech out the faq at the top of the page it will answer your questions.