An SEO will trim to bottom surface of the roof if the wall is below (as in your image) and to the top surface of the roof if the wall you are keeping is above the roof - so may no be suitable for what you want.
'Connect > Trim to roof or shell' should do what you want but the strengths of the Building Materials come into play here.
Stronger BMs will cut weaker ones.
So the BMs in your wall need to be stronger than those in your roof, but the top skin of the roof composite will need to have a BM that is stronger than the wall BMs.
Otherwise the wall will completely cut the roof which is probably not what you want.
Barry.
One of the forum moderators.
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