Run 9 setups.  Each number below is a setup for 2 runs.
1.  Measure mirror plates on
2. Remove mirror plates and reinstall.  Install bottom two screws first, then middle then top
3  Remove mirror plates and reinstall.  Install middle two screws first, then bottom and then top
4. Switched top plates and bottom plates.  Install bottom two screws first, then middle then top
5. Measure again no changes
6. Switch upstream and downstream plates.  Bottom and top plates put in proper places. 
7. Mirror Plates off. Stand Temp different
8. Swap back to original positions. Stand Temp different
9. Swap back to original positions. Measure again. Stand Temp similiar to run 1