Since I couldn't find anyone to try them out with, I pulled the trigger anyway.
I installed the brackets yesterday and my wife climbed on board for the first time last night.
She needs to use my footpeg to climb over, and it still requires a bit of gymnastics. However, once she's on board, she fits fine. Snug, but fit.
We really look forward to going away for the weekend soon! Between the E55 topcase and the two E46s, we can carry a lot of stuff.