Question
Is it possible to merge an existing surface with a final design surface?
Answer
Yes you can and very simple it is to, just create a new surface, name it in line with your naming convention go to definition/edits and then select paste surface select your largest surface, then repeat with any other surface you want to merge with it, you can then style it in the normal way as an added bonus it is dynamically linked so
should any of the surfaces you have pasted your merged surface will update.