I don't think that the thickness of the Structure should change just because you switch from Vertical Risers to Slanted Risers. Usually what happens is the bottom of the structure goes a bit lower because of the slant, but its thickness does not change.
Can you give me steps to reproduce this?
About the Floor Plan Display of those Slanted Risers: Unfortunately, it is currently not possible. The GDL Objects responsible for generating the Stair Grid is not scripted in such a way. I think it could be done by modifying the script, but currently it is not scripted that way.
You could make a wish for this and we could submit that to GRAPHISOFT for consideration.
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