Hi Steve,

> There is a Flip command but I can't make it work.

The flip command doesn't do anything on a closed solid, because there is a mechanism that performs intersection tests on solids to determine the outside.

But that mechanism can get confused if there are self-intersecting surfaces in the model, which there was in this case - the side wall portion of the green piece is a surface with a bunch of control points in it and it folds back over top of itself near the tip.

If that area is repaired to not have a self intersecting surface (see attachment above), then things will work properly with it.

- Michael