I don't have that light, so I can comment. But, I do have a 58, and I have 2 bulbs over it. ( 175 SE ), using a full Hamilton hood, so it sits on the tank.
You could get by with one but there might be darker spots on the ends.
Here is an older picture of mine, only the left bulb is one, and you can see the one side is darker. Granted it isn't centered and is high above the tank, but gives you some food for thought.
And here is a picture of my 29 (( only 30" long )) with a single 250 over it. It is a current fixture with only MH, but might help too -- the corners are darker, but I don't maid too much. And if I really wanted to could hang it to get better spread.