>> What is the advantage of these big planes?

>It makes for more uniform behavior with generating planar end caps. With curved outlines an underlying plane surface that hugged directly to the trim edges would have a couple of places where the edges touched the edge of the natural underlying surface at a "grazing tangent" point which isn't necessarily outright terrible but it makes for some more work to be done in some kinds of intersection processing.

Ok, understood. Perhaps a heuristic could be used that only creates the big planes in cases where they are needed? The consequences of having them are a little hard to grasp, particularly for newcomers, questioning oneself why certain operations have no effect.

>If you like you can select your cuboid objects, then type Tab and type in ShrinkTrimmedSrf and push Enter. That "ShrinkTrimmedSrf" command will shrink down those wider planes.

That is a good shortcut to get the object into the shape I want - now show points works! Like with manually replacing the faces with "close fit" faces it removes the link to the construction rectangles - but that's ok.

Thanks, great support, as usual!