Hi Ezra,
Sounds like a great project. The Twigg pistol lock looks fairly large which is a good thing. That means the internal parts will have enough extra metal to make drilling holes a lot easier. The small locks have such close tolerances and with the inevitable shrinkage from casting from original copies it makes it very difficult to drill holes without having to add metal by welding. I think if I were making pistols with small locks, I would order the lock plates, cock, frizzen, and feather springs and then make all the rest of the parts. Good luck.
dave