K.L.Davis test are to determine flex in the receiver.
His results have shown some interesting results.
The amount of flex on a receiver with hanging 20 lbs on the rail system,
then adding heat showed flat top receiver flex / movement as much as .016".
Adding heat to the testing helps to test as if the weapon system is operating.
It will be interesting to see the results with the use of a vertical grip.

His test results show that a carry handle upper has less flex / movement of the receiver when hanging weight. The carry handle upper only flexed / moved .0015". I beleive this is because the bridge support of the carrying handle. I hope his test results will help to prove why.

What's another interesting point of his test in his very rigid looking fixture. His fixture looks to be stronger then any lower receiver I could think of.
I would have to assume his fixture would help to reduce flex / movement of the upper receiver during his testing, compared to using a standard lower receiver.
Keep up the great work K.L. Davis. Your test result could help to improve product designs.
Best regards,

Frank
POF-USA