The boys at HP shoot during the summer. So they do their work in the winter. There is also Butch Hongisto. He is a kinda hard to get a hold of but does good work.
There is currently a thread on Rimfire Central regarding 52C triggger alternatives and includes sources for individuals who can lighten the C trigger to +/- 4ounces. I don't know how to post links but the thread is titled "Browning 52 Repo" by Bolero. The Repo is not a typo and is in fact part of the title. This thread is on the Winchester Forum in the 52 sub-forum.