Buy 1 copy of Helm's Deep (once it's available where you are) and all of your hinge problems will be solved! Plus, you'll get a lot of other great castle pieces!
It comes with 19 of these:
Not to mention 40 of the "brick" bricks in lbley
PS, I really like your troops and wall tower. Have you considered putting some columns of 1x1 round bricks in each of the "cracks" at the corners?
Stephle59 used that technique really well in Archenval, as seen in this picture:
Keep up the good work! I'm off to read the stories for your GC entries