When youve got the top burr carrier screwed down and its near the proper zero point, try wobbling the hopper from side to side and front to back. If the burrs are touching when you move the hopper into a certain position, the teflon tape may help. If the burrs dont touch when you do this, congratulations, your machine is nice and toight :).
I dont know if this mods on the CG site are limited to people with older machines, or if they got a Monday or Friday machine ;).
All the best.