Hi tcas, Chris from Worthington Assembly here.

We found that when we switched to our super fancy high end reflow oven (that's literally 15 feet long) all those sorts of issues kind of went away. Stencil design has a lot to do with it, believe it or not. Too much paste on the center pad and the QFN just floats up and the joints never get connected. So yeah, if CircuitHub just has a footprint for QFN's that's known to work, you can eliminate a lot of that type of research.