Eric,
Great looking rifle! I too live in the humid and rainy South and I do not think there is any way to stop rust on everything down here from tools to farm implements. I bought an air conditioner in my shop area would prevent it but with the heat and humidity, even with air, things still rust. Like was mentioned as I am working on a rifle, and come back the next day - there it is again - slight surface rust everywhere you look. Seems we just have to live with it. Just RIG your bores and press on. On my son's rifle of which I have been working for several years, the barrel was rusted when I got it and I am just going to use it to my advantage of "aging" the rifle as I finish it. We just have to persist! Maybe that is why you see very few surviving longrifles in the South and that is the ones that were used, all rusted away. Good luck and a again a beautiful job on your new rifle.
elkhorne