This may be due to the strong bleaching out of any information you had in the highlights to begin with. The file you use as an example looks a little hot to me as if the highlights have bleached out. It could just be my monitor though.
As for the bleach time Thomas, it varies depending upon the feel and color I am looking for. However as I said before, what I have noticed is that the first bleach bath doesn't do as much as subsequent ones. I also use the bleach in a warmed state by floating the bleach tray in a larger one with warm water. To use your words...
"Experiment, experiment, experiment" !!