When beveling a nurb cube, is there a way to keep the sides the same size so only the corners shrink? If not, what is the mathematical relationship I can use between extrude and size to keep the sides constant?

I think it works the same as it does for meshes - in other words, non-proportional scaling (required for beveling), isn’t supported. In fact, there might be the answer to your second question…blender scales everything in proportion. Remove the proportion from the equation, and you might be left with what you need. In other words, size this object (the bevel), but only by moving each vertex an equal distance along the x,y, and z axes.

I’m not sure I got your point, but to malke corners shrink without changing the definition polygon in a nurb curve you have to increase the weights of the vertices.

The higer the weight the closer the curve gets to the vertex.

Stefano

So what you are saying is blender cant do it, and I would have to do something by hand. This will make my work a lot harder.

I do not know why nan did not give you this needed option. I hope they come back and fix this.