Sorry I don't have Archicad in front of me at the moment so can't test it myself.
If changing the contour pen in the wall composite changes your RCP as you want then you need to create a second pen set that is used with just your RCPs.
So leave your composites as they are so your regular floor plan is correct and use your regular pen set.
Duplicate that pen set for your RCP and make the pens used for the wall contours thicker as you require.
Now every time you swap to your RCP you also swap to your RCP pen set.
This can be automatically set up with saving views of your plan.
The pen set is saved with each view.
So save a view of your floor plan using the standard pen set and another view of you floor plan as the RCP using the RCP pen set.
These views when placed on your layouts will now automatically be using the correct pen sets.
Barry.
One of the forum moderators.
Versions 6.5 to 27
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