EDIT: Join was not the culprit, offset was!
I’m constantly joining and splitting surfaces to see if there’s any gaps, check curvature, add fillets etc. etc.
What’s hampering this workflow is Rhino’s weirdly uneven idea of shrinking joined surfaces. Sometimes, it shrinks it right up to the very edge of the trim line, which can make it difficult to re-trim after extraction, and sometimes it does leave a millimeter overflow (like other CAD software does), but this feels random (I often leave quite a large overflow).
Is there a setting somewhere to control this?
Ideally, I’d just like the Join command to leave my surfaces alone and not shrink anything.
(Also, unless I’m imagining things, sometimes trimmed fillet surfaces seem to get extended too…)