ScalpelJunkie I own a plastic version of Kaweco Sport with a clip and it holds as if it were there since day one. Granted, the brass version will be heavier, but knowing how well this is made, I wouldn't be afraid the clip would come off. However, if the German build isn’t that impeccable, you could always give a slight bend to the clip’s octagonal ring (it’s open) so that it wraps the pen with a little more force.
ScalpelJunkieMe personally, the clip doesn't stay on very well. More often than I'd like the pocket clip would fall off of my pants and the pen would fall back into my pockets. Maybe my clip just has really poor clamp but who knows.