One note: My layout is of the shelf type, with the shelves just sitting on the shelf brackets. There is a 90 degree corner to the left of the bridge, and it has about 1/4" of play - meaning that I can push the shelf back when putting the bridge in place, then I can wedge it up against the bridge when I'm running. This makes taking the bridge out quite easy too, but it is stable when I'm running trains.
The shelf that I move is 27 feet long, so the 1/4" is very little movement when compared to the radius.