Excellent suggestion Alex - never occurred to me to shim the router. I was focusing on the router plate.
@TMToronto - I will run more tests for tonight. When I mentioned backlash earlier, I should have noted I was getting highly repeatable results with the machine returning to the same position, but I did not measure it beyond eyeballing the position. And I learned that precision is for measuring systems - the appropriate term for motion systems is repeatability. TMYK 
-Tom