Hi Bravlin, I took a quick look at your 3DM file and it looks like you're doing a Loft instead of an Extrude perhaps?

The curves you are lofting between have some skew between them, so that's going to affect the accuracy.

I could see the skew by looking at this edge in the Top view, a completely vertical extrude should only show as a point in the top view:





And it looks like the top and bottom curves don't have aligned endpoints:




That method I showed previously is only applicable to reverse engineering a completely vertical extrusion surface, not one lofted between 2 slightly different curves.

- Michael