BB shell width is almost exactly 68mm so that isn't the problem..
Then I would put the spacers on the NDS only. My Rotor Power needed only 1 x 0.5mm spacer compared to 2 x 0.5mm for my 3DF on the same frame, so I think there may be some manufacturing variance on the Rotor axle lengths??
Yes it must be that there are differente lenghts.. Strange!
I've put a 2.5mm spacer between the BB and the frame on the non drive side and the play is gone. If I turn the preload bolt very thight, the crank has too much friction but when I turn the bolt halfway, it turns nice and without play. So I think I'm fine now, or does the preload bolt need to be tightened all the way?