Non-planar quads: how to connect two curves with faces? I am trying to create a specific shape consisting of two curves connected together by faces (in the context of modelling a plane).

Here is what I came up with by converting the first curve to a mesh, extruding to get the second curve and applying some transforms (rotating and scaling). 

The problem I have is that because the scaling is not uniform on all the axes I get non-planar quads which get triangulated by Cycles: 

I thought of different ways of fixing this:


Creating and converting the two curves separately gives a similar result
Dividing the quads by adding intermediate curves makes the quads flatter but it is not perfect


I know that it is mathematically possible, for instance if the algorithm converting a curve to a mesh divided the curve into segments according only to the angle and not the distance between vertices, so that's why I'm asking: does anyone know how to do this "the right way"? Thanks!
I tried to re-create your model to mimic the issue and as others stated in comments, adding some loop cuts should solve it.



After that I would just try to make the cuts more even using vertex slide.