The part I don't understand is that in my experience, with 6 TIG frames in a row now, is that if my jigging is right to start with then things hardly move during welding. Certainly nothing like that far. And in the case of this Trek, the HT and ST are still in parallel planes (which is what matters much more). If the cause were welding distortion then it would be all over the place. So the most likely cause is just poor jigging. But you would think that in a production environment the easiest part would be to give everyone a decent jig where you just throw the tubes in and they're automatically in the right places.