Need help with light configuration

I just bought a 75g tank for reef, with stand and canopy. The canopy
has no lights so I am mounting my own. My plan is to install 2 VHOs,
one in the front and one in the back, and 2 MHs, one on each end
between the VHOs. This sound like a decent configuration ? What I
need to know is :
1. What wattage lamps are recommended here ?
2. Is there a recommended distance from the water surface ?
3. Do I need to install a fan or two in my canopy for the heat ?
( My canopy is not totally sealed, it is open in the back and on the
top across the back ).

Advise welcome Thanks.