Opinions...120gal tank = MH bulb positioning

[Delphinus]

This tank has a 48"x24" footprint, no? I'd go perpendicular since you should have the room for this.

The lighting you describe, is what I have over my 75g. However since my footprint size is 48"x18" I don't have a lot of extra room so I have to run my lights parallel.

I beleive that the reflectors used for perpendicular mount, are more efficient, i.e., they have a much better spread of light and more light is directed downwards, etc., so if you can use those, go for it.