Hi Barrie, I played around with this for a while with no good luck and I think you may not be able to get rid of that lump with your sections in their current shape.

I think the problem is in these sections here:



This one is I think too high for this particular surface construction:



To get rid of the bump the sections will need to make a more gradual transition in the area of the lump, I think that will mean either lowering that indicated section a bit, I'd try just slightly scaling it down in z a bit, or adding in even more sections so that there is more of an even transition between them if you need super high accuracy to some existing design. Too many sections can also easily add bumps as well as it adds a lot of pressure on the generated surface, if the transition between sections is wiggly in any way.

It does not take very much compression of change to result in a visible bump is basically the problem.

- Michael