Congrats David!? Finding a cold solder joint is usually very tricky.? Well done.?
You are right about the FT-980 RX quality.? The low noise floor is the most notable parameter.? The selectivity and IMD are not as great but acceptable.? You will definitely enjoy this rig, especially if that cabin is an RF quiet location.
One important mod that I would recommend while you have the radio on the bench, is the memory battery backup circuit., authored by F5RCT.? This file is in the mods.dk repository but if you want I can send it to you directly.