Hi Bruce

I have to disagree with closing down of lens to create depth of field for better sharpness.

All enlarging lenses that I have ever used are Flat Field lenses and therefore are designed to focus on a singular plane.
There is possibly some depth of focus issue, that may be present, but and image will be as sharp wide open as is closed down two stops.
Depth of field is apparent with image taking lenses in the camera.

I do recommend not using the smallest or narrowest apeture as the light will diffract and cause softness trying to get around the apeture blades.