OK, lets get to the reason you have a bracket off the starter. In '96 Harley decided they needed this to stop the factory pipes from cracking at the "Y" pipe. The weld would literally fracture because of lack of support. They then offered it as a retrofit for older models. This solved the problem of the stock pipes fracturing, but does not address the way Rhinehart has designe their mounting. I saw some issues in the way the local shop mounted mine, and loosened the entire assembly. I removed the mufflers first, and immediately noticed how much the heat sheilds were binding just to fit to the pipes. I did not pull the head pipes, but rather took all the stress off the mounts including the mounting point of the pipes to the heads. Once I had everything so I could move it, I tried to let everything align naturally, and kept alternating between the head pipe mounts and the starter support tightening a little more at each point. So far at 6k I don't see problems.
As far as running with the bolt loose at the starter, I would believe you will be creating more stress on the pipe, and possible damage to the finish on your inner primary if the pipe were to bounce against it. Now having said that, the issue I see with the Rhinehart design, is that it doesn't allow for the movement of the motor on the rubber mounts. One of the things I have noticed is that the mount under the front of the motor is acting like a piston to relieve motor vibration, thus as the motor is flexing vertically, the mount on the pipe at the started is stressed. I don't know if I will still have a fracturing issue, but I don't believe the design allows for another option if you allow the pipe to "float" at the starter mount.