I have a Mamiya 6 Automat folder, and after two fixes by myself, it can make accurate critical focus and produce tack sharp photos. The Mamiya 6 is well designed with its unit focus mechansim by moving the entire film back, so if the focus is properly collimated can produce as good results as any folders of that era. I scratched the half-silvered mirror while I tried to clean the VF/RF, so in the end I bought a new custom-cut mirror, replaced the mirror, and did the vertical and horizontal calibration. I'm just an enthusiast with limited experience, so a proper technical should be able to get yours to work properly without much trouble. Here are some test shots:
Explore this photo album by Zheng on Flickr!
flickr.com
I also wrote an article comparing the various low-cost 6x9 folders in this 35mmc article
Explore eight 6x9 folding cameras to find the ideal travel companion with compact size, light weight, excellent lens, larges negative, and simple operation.
www.35mmc.com