This never really got answered in my post, but does your stem have some play at the folding part when tightened down? I found that the bolt holding both parts is smaller then the hole by only a few thousandths, but enough to be noticiable. This is not the same as flexing. I limited the movement by putting a brass shim around that bolt to take up the slack. Just curious as the Downtube 9 is my first folder too.