Not sure where you could be getting chronic creaking. I have probably have at least 2 dozen quill equipped C+V road bikes with many different stem, bar, headset setups. Some old, some new, overhauled and not, a few slightly undersize and everything in between. Not a single creak, anywhere, can't imagine ever converting any of them to threadless.

Are you working on these yourself? We really should be able to help get to the bottom of this I would think.

This really limits your options and eliminates a lot of very cool C+V projects.