If someone is really annoyed by the presence of PE, in my opinion the much more cost-effective way to minimize it is illustrated here:
http://groups.yahoo.com/group/EQ6/ph...78408/pic/list
To polish the worm, there is no real need for lathe, it can be done with simpler, ad-hoc arrangement.
Also, the replacement of original gearbox (or total elimination of gears between motors and worm gear by using timing belts) does help a lot, some reports are talking about 5"pp and even better (for EQ6).
However, as Peter said, all this *will not* correct for items on his list.
So, all this effort does not make much sense .. when at the end, some sort of guiding is still needed for longer focal lengths imaging.
This discussion reminds me of a similar thread, about direct drive stepper motors on both shafts.. like ideal solution for ideal mount. Yes, we can and we should aim for the better.. but we have to take into account the cost of this, sometimes irrational urge... IMHO of course.