I've been using a Rollei SL66 for some years too.
The speed of film cranking and the emulsion thickness seems to determine film overlapping for me. I'm lucky to get 12 images on a roll. I think Rollei had future-proofed their cameras by ensuring users expend more exposures to keep film afloat.
That´s right. Until now I only used Fp4+ and Hp5+ which are of
a "classic" thickness I think.
As I remember the film crank should not be moved to fast, because
some of the metal spools in the mag could lose diffraction and
the frame spacing decreases. I think I´ll make some experiments