You guys are over complicating it. I'd put the bars in the vise on a mill with a clamp around their center (as they are clamped by a stem), put a dial indicator against the end, and push on the end of the bars with with a known load. I could set this up and do it in about 20 minutes. I happen to have Deda Zero 100 bars on my bike, but no access to the Ritchey bars in question for comparison. However, FWIW, I don't believe bar flex to be an issue and as such, no interest in setting this up and doing it.