This is a pattern I originally designed for my nephew.
The gauge is not particularly important. I’ve made felted versions of this pattern that have come out fine; my advice is to attach the back plates and assemble the thagomizer before felting it. (Felted versions of the pattern will probably require 2-4 fewer back plates.)
If you have any questions about the pattern, or if you notice any errors, please let me know by sending me (jwgh) a comment via ravelry mail.