No they wont be too long. People run the 906's with the bilstein 5125's (F4-BE5-6252-H5) all the time. That shock is 21.54" extended, plus the 1" stem adapater for that shock, so extended length with those is 22.54". And there is no issues with the 906's coming unseated.
To the OP, if you go with those 5100 shocks (24-100144) you will need to change out the lower bushings. They need to be 3/4" bushings.
Those sound like a good shock. If you can get the 3/4" bushings for them I think they would be a good option. Otherwise the 5125's are always a good choice.