Tightening Top Yoke Nut

[Fazerider]

I don't recall having that difficulty when I did mine, and there shouldn't be much difference between the 600 and the 1000 from that point of view.
I had the bike on the centrestand and propped so that the front wheel was off the ground and pointed straight ahead and just torqued it up, with my left hand braced against the left handlebar. You're not using the r/h endstop and bracing against the bike itself are you? Can't think why it would twist otherwise.