Bruce the guy from Pa that sells prints to make your own flowbench and supplies to do so did the “pass around challenge” where he made up. Calibrated plate and sent the around to whoever wanted to join in. Only he knew what the true numbers were on the plate and then everyone sent their numbers in. Much cheaper and easier than shipping a head around the country. That is what made me sell my manometer bench and build my third of three benches I’ve owned