I think that unless one has adjustments available on each of the three stages that there reaches a point of image degradation through diffraction. At least that has been my experience. When one tilts the paper easel, then unless you have adjustable lens stage and negative stage you are confined to stopping the enlarging lens down. Enlarging lenses have the same limitations so far as diffraction that taking lenses have.

I have one enlarger that I would not consider doing this on (Saunders 4550 VCCE)...another (Durst 138S) that would allow me to do it with ease.