I have a DCR lens, a Lumagen Pro and a 2.40 screen. Set all sources to output 16x9. I set output aspect ratio as 2.40 and input as 2.40. Using a 2.39 movie, you adjust zoom to just fill the screen on both sides. By doing so, you will have some over-scan top and bottom. Using the same amount of shrink top and bottom from the Lumagen ensures you get the most image possible on the screen. You will get somewhat more or less over-scan top and bottom from using combinations of 2.35 and 2.37 input and output aspect ratios with a 2.40 screen. My 1.78 and 1.85 images are properly sized using 2.40 input and output. There is no other way to set this up correctly.
I have had the combination of the DCR lens with the Lumagen Pro since the beginning of the year. I would not be without it. I watch a lot of movies. Lately, it seems like 3 out of 4 are 2.39 AR. What the lens does for 2.39 movies has to be seen to be truly appreciated. No negatives, just all positives. If you have a 2.35 or 2.40 screen and a Lumagen Pro or a Sony 760/5000 you really need to try this. I cannot imagine you will send it back.