2mm is way too much. About 1mm should be good. Being a mechanic, I've had to freeze and fit bearings and the like before. But that is metal to metal so there is no "give" in the materials. Wood allows more give as the fibers will crush more around the hole as you are fitting the post. I reckon between 0.5 and 1mm should be ok. Anything outside that and it could be too loose or too tight. Remember though, if it is too loose, you can always wrap the posts with plumbers tape, etc as a fix. Just try drilling in stages to get the best fit. I did it with my ES and got it right.