Been doing some reading on balancing Larry and wonder if the product on the following website might be worth trying. Different ways to center the wheels on the lugs including removable centering pins or attached sleeves.

Obviously nothing magic, in fact it is very intuitive and they seem to have a satisfied following of real people on their testimonial page. Sounds like several customers have gone through some of what you have and this cured their problem.

Cheapest looks to be "solution A" which is the 3 pin removable centering kit for mounting each wheel. Sounds like a reasonably inexpensive means to eliminate one potential variable.

http://www.tru-bal.com/index.cfm