Super Chromega D4 focusing problem with 150mm enlarging lens
I recently purchased a Super Chromega D4 with small, medium, and large format lens cones. I am having difficulty focusing 4x5 negatives. The cone is 5 1/4" but has a 135mm Rodenstock-Omegaron lens mounted on it. I have my easel raised up an inch as the manual instructs. I have done quite a bit of searching around for an answer as to why. I BELIEVE that it is because the cone (and the auto-focus rail) are for a 150mm focal length. I have a shorter unmarked 2 3/4" cone that came with this enlarger, but it must be for a different model enlarger as the circumference of the cone is slightly larger and doesn't fit. I was hoping that this cone, although too short probably, would at least allow me to focus. I have used the enlarger and the 50mm lens mount with 35mm with no focusing problems.
I found on the classic enlarger site that a D3 requires approximately a 4 inch cone for the 135mm focal length lens. Nowhere in the Omega literature can I find a listing for proper focal length for each lens cone. I have tried registering and searching on this site but have been unsuccessful thus far.
Most likely I will want to buy a superior lens to the Rodenstock-Omegaron, but I wanted to at least try it before I cast it aside to the useless lens pile.
Can anyone tell me if I am correct in my assumption that the focal length is wrong. I don't want to go ahead and buy yet another lens and find I didn't need to.
I would really appreciate any help. Thanks!!