First, I'm not the great builder you are referring to, but I am cautious. I try to have a spare frizzen for each lock so that I don't get stuck waiting if somethings goes sideways. Just buying individual parts, they are, like Tom said, soft. After the spare frizzen is filed to shape, and mostly filed to fit the pan, I take strip of 220 wet and dry, wide enough to cover the pan, and close the new frizzen on it, rough side up. After a couple of strips and maybe 15-20 passes over the pan and under the frizzen, the fit is pretty good. Use lots of WD-40 to make certain the process is good and messy. Some thumb pressure on the frizzen helps the things along.