Keep offset brep naked surface edges planar with original breps

I’m having an issue with an open brep offset. When I offset the brep I want the new offset brep to keep its naked surface edges in the same plane as the naked surface edges of the original brep. I know the reason that its not is because the component is basically offsetting each surface according to its normal but I don’t know how to accomplish what I’m wanting. Any help would be excellent. Thanks in advance for any insight.

Maybe a better question would be how do I select only the naked surface edges so I can extend them and then trim them with a plane? (10.5 KB)

Dear @ken.marold
what about using “cap holes” (native grasshopper) to get a closed polysurface, then perform the offset with “shell polysurface” (component from pufferfish)
explode / deconstruct the brep, identify the connecting surfaces and join again ?
… hope that helps - kind regards

This might help.
Anemone used. (16.6 KB)

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Thank you! That worked perfectly.