Chrome will show all the imperfections of the metal underneath; the underlying metal has to be polished and smooth if the plating is to look the same. Most chrome that wasn't intended to be seen (and is covered with paint) is never going to look as good as plating that was intended to be seen. Of course, you can't tell unless you remove the paint... I don't believe there are differences in thickness -- I'm pretty sure that can't be differentially treated during plating of an entire frame part.