Hi Larry, yes that's not really a bug in the dimensions, it's like Brian writes above that the edges are not being recognized as arcs.

Currently MoI looks at a curve and in order to be recognized as an arc it must have the same curvature (within a very tight tolerance of 0.0000000001 units) at 10 points sampled along it.

Meanwhile the result of the boolean is calculated at an intersection tolerance of 0.001 units. So this mismatch between the "is it an arc" tolerance and the "surface/surface intersection tolerance" is one problem.

But also there is a mechanism that does special case intersections between analytic shapes to get higher precision. However, I have disabled the sphere/plane analytic intersector back a long time ago though because of some bugs in it.

It's pretty risky to modify either the tolerance or the surface/surface intersector right at the end of the beta cycle, so this is something that I can look at fixing in v5 once that is underway.

- Michael