Saying that, I have just discovered an offset Surface command.
So by copying the line up by a specific distance and then lofting the 2 lines I create a surface, which can then be offset and it appears to keep the Z value and the correct parallel distance.
From the offset surface I can drop them back to lines, delete what I don't need and create a complex chain or trace the required surface edge with a new line.
So by copying the line up by a specific distance and then lofting the 2 lines I create a surface, which can then be offset and it appears to keep the Z value and the correct parallel distance.
From the offset surface I can drop them back to lines, delete what I don't need and create a complex chain or trace the required surface edge with a new line.