You might want to verify using a test target with each camera . . . found here, and elsewhere on the web. Printed at 8x10 using a laser printer, it should work very well. At some point in the process, be it the negative stage or the printing/enlargement stage, a test target pattern on film could reveal any problems resolution-wise. It could also reveal problems involving contrast. Are your lens elements (front and rear) free of finger prints, mold, fungus, fogging, etc, anything that could interfere with sharpness or contrast or both? This would also include the enlarger lens. I'm assuming here that you're not using the same lens to print 35mm as 6x7.