A freighter version for the -400 has potential because the workload to produce that is "relatively" light. The -500, being a shorter variant would require a much more laborious effort to change both the 3D and the flight model, being geometrically disparate...and the return on investment in that, I believe, probably would not justify the efforts. While I think a freighter variant would appeal to a statistically smaller set of customer use cases, I recognize that there is still a place for it...and so I do want to do a -400 freighter at some point.
..and yes, I'm still working on the 733 every day...my carpel tunnel and "tennis elbow" remind me constantly. I think I can safely say at this point that we'll definitely put out a more informative report this week on whats going on with the development.
-tkyler