SEO on Mesh by Column kills Mesh

[Anonymous]

I am working on AC11 build 1114 on XP. I am trying to use SEO to cut remove a column from a mesh. This way it shows up correctly in section. However It Causes the polygon to fail and I get a Very Odd result. I get a "skin across the hole that was created. Any Ideas from anyone why this is happening, or what to do to fix. The only thing that I have found to do is to create a circular hole in the mesh and then fill it in with a circular mesh at the right height. This does show up correctly in section.

[Anonymous]

Try subtract with upward extrusion rather than subtract.
If the column is exactly the height of the mesh you
might get this result with simple subtraction.
Peter Devlin