I used to own a ME Super, nice camera. I gave it to my niece who destroyed it. Anyway, one of my cameras is off by an f-stop too (Rollei 35SE), always has been. I do like you suggested in your post, I just set it to 1/2 the ISO.
I think that's what I'll do. Just set at 1/2 ISO. Would I start with the developing time for 400, as opposed to the shorter developing time for 200?