I only read the first 80 posts, so this may have already been addressed.
Most planes getting painted have not had a measured weight and balance since the last paint job. All the mods, repairs, and removal's since have been calculated, and the odds of an error is well above zero.
The club painted planes over the years, and we had a measured W/B each time. The change was significant on all of the planes. W/B measurements are not expensive, and good choice if it has been 10 or more years since the last one.