I've been thinking about doing this and even with the project 321 steerer tube I can only see a few ways of doing this. The headtube length is soo close to the standard crown fitment that you need a headset type like cannondales where the bearings sit inside the headtube completely flush as there is only about 1mm to play with, or machine down the normal bearing cups so they don't stick out either end of the headtube. Trek have informed me that bearings cannot be pressed directly into the headtube so looks like the machining route would be best. Or you could go with the lefty that has the max crowns which will give you about 3cm of clearance to play with but then your gonna have a big ugly stack height which will look a mess with lots of spacers and also risk messing up the geometry of the bike, this way would be very easy and work fine I believe but to usea lefty with standard crowns to get it looking sexy and flush its gonna mean making something and a bit of work and also the testing of a new conversion and as mine is a 2010 fuel ex 9.9 so carbon this could be less of a safe conversion than if it was metal so will test carefully but if it works will make a greak bike even better and look sediment, failing that or if i chicken out ill just stick the original headset in and use the fox fork.
People thoughts on this would be greatly appreciated.