Can't curve and fair a loft

I’m having a major problem that I can’t seem to get past here. I have a surface loft that needs to be developed into metal plate. I have read that using a loft and specifically the plugin, D. Loft produces reliable results for profiling.

I’ve included the file below, I am using the top and bottom edges but trying to have a convex curve in the middle all the way along, while maintaing fairness. I have inserted 3 rows of control points and used Move UVM command and smooth to try and create a curve but it still looks like it’s too edgey and nowehere near as nice as just following a curve like sweep 2 rails.

Is there a way to create a smoother transition here on the curve while keeping this as one developable surface? Would Solidworks be a better option for this?

Example.3dm (1.1 MB)

Given the shape of the two long edge curves which become parallel a developable surface with curved sections along the entire length is not possible. That is how developable surfaces work. It is not a limitation of the software.