I think that's a good call. You can have two walls 5 or 10ft apart but it would be good to have a V shape for arrow slits and windows which bridge two wall sections. Perhaps wall sections with crenelated tops. Most of a castle is in the set tho and with a very small extra few I think castles would be covered. I might try having a pop at doing some castle with them later and see whats easy and whats not so easy.