Making progress. Got the plumbing glued and just waiting to figure out what to do about the light.
My original plan was to run the light on a barn door rail so that I could move it forwards and backwards as needed. It wouldn't be much, but it would be nice to adjust it.
The problem is that the cieling joists run parallel to the tank and the one that is located over the tank, is not centered in the room.
In this picture, you can see the three windows above the old tank. The new tank will be in the same spot, but will be a pennisula style so I want the light (which is 4' long) to extend over the tank. The cieling joists are parallel instead of perpendicular.
My thoughts would be to drill 2 holes in the cieling where I want the light to be, then get up in the cieling and lay some 2x4 across the parallel joists to cross the joists and connect to the 2 holes that I drilled in the cieling. This needs to be very strong and secure, since the fixture weights 55 lbs.