Where to place Control Accelerometer?

Thanks to Mr. Tustin for the ideas he and Mr. Brenner hope to have added to MIL-STD-810G. But I seriously question the idea 'If all agree within 10%, the fixture is acceptable. If not, the fixture is not acceptable.'

I've had the opportunity recently to design, fabricate and experimentally evaluate (using non-resonant dummy masses in place of the eventual DUTs) two fixtures. One DUT has 4 mounting points; the other has 6.

Fortunately, "business" in our lab is very slow right now and I was able to scrap my first attempts and start over, twice on each.

The best I could do (three tries each) in getting agreement between the several accelerometers was 12% on one and 16% on the other.

If this was the best that a lab could do in three attempts. and the proposed words existed in 810G, how could the test proceed?