Some time ago there was a thread about holding the crank while tightening the rotor bolt. The concensus was to put it in gear and crank down the rear brake, either with a helper, or by turing the adjuster nut.
The disagreement revolved around which gear to use. Some said low, some said high. Frankly i don't remember which side i came down on, I just know there were those that said i was wrong. So both sides were represented.
My closing statement was simply, if you're there, use trial and error and pick the gear that holds the best. I have since done it for myself on my current project and have the definitive answer.
Its is beyond a doubt 5th gear that you should use. I used first and could only get halfway to my torque goal before the clutch began slipping. In 5th gear, I could get to the lower level of the range, then the clutch would slip. But that's good enough as I have a lightened rotor. I do have Barnett clutch springs.
If one would want to get to the higher range, one may need to do it on the bench and shove something in the transmission gears.
To get the rotor off while still on the bike, use fifth, the brake, and an electric impact, if a breaker bar causes the clutch to slip. The shock of the impact is good for a tighter bolt. However my same electric impact could not get the torque up to the acceptable range and the breaker bar/torque wrench was needed.
I'll put this in Tricks and Tips.