Is that an f8 65mm SA? I f so, I didn't think it would cover that much.
I did a similar conversion to an Olympus 50mm lens for a focusing mount. As you have probably discovered, it takes a few dismantled lenses until you find one which can accommodate the rear lens element.
Schneider states an image circle of 155mm at f=16, and the 140mm wide image needs about 150mm. The image circle is indeed covered even wide open at f=8 (if you can call it that). The truth however is, that the vignetting is awfull and forces you stop down a lot.
I also have a number of not suitable 50s (i.e. what is left of them) in the drawer...