I often use intermediate ƒ-stops on my Rollei. Matter of fact, that's one of the things I like about it. Kind of like Kentucky windage.
I have often wondered about intermediate shutter speeds.
I almost always set the shutter on the mark except when my exposure needs 1/125 but the dial is only marked at 1/100.
In that case, I set the mark just to the right of the second zero in the number "100."
I figure, if it works, it works. If not, it probably doesn't make much difference. Besides, I'm probably using Kentucky windage on the ƒ-stop, anyway.
One thing I have noticed is that using the Rolleiflex sharpens me up when I go back to shooting 35mm.