Since you have a canopy why not just do a retrofit kit?
You can get two IceCap 660's, endcaps, standoffs, and reflectors AND if you decide that you did want 8 bulbs, you can cheaply add two more reflectors and endcaps. Plus an IceCap 660 runs the 54W lamps at more like 84-86 watts, and very efficiently. 6 bulbs would be enough with an IceCap.
Just a thought.