Thanks for the help. I took a look at the render meshes as per your advice. So this issue is not due to a modeling error but rather the nature of the render mesh function in such circumstances. (Yes?)
I dont know what the “shrink+yes” is relevent to. Is that referring to a trimmed surface as in _shrinktrimmedsurface?
I used a two rail sweep to create all surfaces and then matched the upper to the lower for good measure. Afterwards all was joined, mirrored, connected with lofted surfaces and made solid. As I understand it, you simply split surfaces at the joints of complex and simple ( or create them that way) and then join into a solid when needed.
Also, when you say “March” did you mean match?
After making the split I get a clean mesh but it looks unneccesarlily dense.
Is that result of the complexity of the arcs used to create the surface?