I am looking into buying a metal halide light, but I just realized that I cannot hang it, are you able to just set the light above the tank? (It would be 5.5" above tank, even further from waterline)
My 150w MH fixture came with the legs and a hanging kit. I just used the legs and it is probably about 5" above a 16 gal. and it has been fine.
However, my fixture has two built in fans which are very good at dissipating heat. You will just want to keep an eye on your temp. and adjust accordingly.