Filing on the peg wouldn't hurt the spring, but it probably won't work because of the temper, unless you have a tiny diamond coated file. You may be able to work it down with a small stone. I have a little triangular India stone about three inches long that I would try for this, were I to do so. If a stone will cut it, you can work very slowly working it down to the right size to fit into the hole in the lockplate.
https://www.brownells.com/gunsmith-tools...s-prod9618.aspx It's the triangular one.
If you try this, be careful not to undercut into the leaf of the spring itself, or to leave any groove anywhere. I would not be afraid to try this at all.
SRH
