Read this: http://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=115919&hilit=dura+ace+11+speed
It tells you how to find the 2.85mm in width needed to get an 11 speed cassette onto a 10 speed shimano 7900 wheel without modifying the cassette.
- Removing the spacer gets you 1mm, so only 1.85mm still to find.
- Milling down the freehub end by 1.85mm is possible, but then the centre of the cassette hits the freehub body
- So removing some material from the hub body is required to make things work without rubbing.
An alternative approach would be to mill down the freehub by between 1mm and 1.5mm until the cassette just clears the hub body, then shave down the back of the cassette as needed (if at all). This is likely to be less bother than dremelling the hub body, but means the cassette will not fit other wheels.
Or a second alternative might be to mill the freehub 1mm and then add a 0.8mm washer on the axle and a longer lockring on the cassette.
Anyone tried this? If someone comes up with a kit I think there are a fair few people who would be happy to pay for it.