7 Calibration & Portraits with 150

[Ken Lee]

Sorry if this is often-asked, but I have read that on the Mamiya 7, the 150 can be a challenge to focus, and that the rangefinder needs calibration. I am thinking of getting a used Mamiya 7 with normal and 150 lenses. Is there something I need to know, especially if I buy it over the web ?

Also, does anyone have any sample shots taken with the 150 - particularly any portraits ?

Many thanks !