I'm having a bit of trouble lining up the castle 'outside' wall pieces - gaps appear at corners, and I can't work out how to fill them in.

There are some corner pieces available, but they don't seem to finish the job for me:
- castle_wall_outside_corner_01
- castle_arena_merlon_inner_corner
- castle_arena_merlon_outer_corner
castle_wall_outside_corner_01 is a small piece that is difficult to fit into that gap, but when it does, it only covers up a small part of the gaps seen in my screenshot.
The two 'merlon' pieces seem to sit too far outward, and look as though they could be for decorating castles like the big one in Sleet Island in LoG2's main adventure.
I've tried changing the elevation of these, but I think I'm just not using the right pieces or something.
I've placed one of the merlon pieces near my wall, to let you see what it is. It does look like the elevation's meant to be changed on that piece, but I have tried, and tried placing it on the inner squares of the castle wall, and on the outer, and tried all different orientations.
Can anyone help?
Thanks