"rigidity under load"
"matching performance characteristics"
These are pool cues, not test tubes. I can copy the exact size, weight & shape of the shaft, but this mumbo jumbo is not controlable. We cuemakers don't have laboratories, where we can jubject a shaft to a berage of tests, before we deliver it. You can't even get 2 engines from a 500 billion dollar car company, to meet these kinds of standards. Dealing with wood, is nowhere near an exact science...JER