So I gave DotTune a whirl yesterday on my 17-55. I followed the procedure on the FM link and got a successful focus range of -14 to +8 for the 55mm end, and -10 to +16 for the 17mm range. So, slightly wider range for the 17mm end, which makes sense.
The average for the 55mm end is -3 and the average for the 17mm end is +3. The average of the two is of course zero, and I am guessing that the lens was set up perfectly at the factory in terms of being balanced between the long and short ends. I am an engineer and I will follow my profession's credo and since the lens is tack sharp, I will leave it the *@_* alone.
All in all, the method was very straightforward. I might try this out on my 100-400 later today. I will need to stick the pattern sheet on my car window and do it in the parking lot. My residence, palatial as it is, does not have any 20m clear lines of sight..