I've had a couple different tank bags on my 1100. I'm currently using the "oh-my-gosh-that's-a-giant" Nelson-Rigg CL-450 that I've
"modified" a bit. My old Eclipse bag is literally falling apart at the seams, so it will be pitched. I have been looking for a smaller bag to use for day-to-day riding so that I can keep the giant CL for trips.
As stated above, the 3point bag can easily be moved out of the way while fueling up by letting it hang on the front two mounts. And with a bag the size of the CL-450, it's good to be able to move it slightly from side to side as it WILL interfere with full-lock turns when centered.
One thing I've been meaning to do, which I saw on one of Uncle Phil's STeeds, is to make short straps that attach to the 2 front "tank" bolts (the one's that are up near the triple tree/frame neck) instead of looping the strap under the frame neck. It would also be easy to make a strap adjusting piece that would hook over the stub on the tank that the seat hooks on to.
Also, if you pull off the seat, there are wire loops on either side of the fuel tank (handles to pull it out?) that the rear strap can be looped through (if it's long enough).