Let me say that they're are a lot of wisemen on this site that have forgotten more than I'll ever know. I;m a noob and I don't even grow.
Anyway, as far as mounting the light screw some circle hooks into the ceiling and let gravity straighten out the rest.
With height in mind I'd def go with an autoflower strain. Auto AK47 x Auto Blueberry or Auto White Moscow both finish on average bewteen 10-18 inches. Obviously with diff phenos shit happens and they can get big but you get the point.
The way I look at it is you don't have a 10x10 room so you're not expecting pounds. Find you some good autoflower (short height/fast finish) strains that you like and SOG them under a 150w HID. I think you may be able to get away with a cooltube and a couple inline booster fans. Or splurge and get a small can fan and be set. That will require some planning on where to cut but you won't be able to get away with not having good air flow to keep the light cool.
I'm a huge HID advocate and I don't think I'd (hypothetically) grow unless the conditions supported them but if I were to drop out of society and live in an RV I could see the need to change my mind and go CFL!
In all honesty you're working with such little space you may want to go the CFL route. They require minimal cooling/ventilation and with such a tight space you could probably grow a couple ozs every couple months or so.
Sorry for the ramble. Hope this helps.