Thanks for the heads-up! I may build a knockabout pair to ship. Third-party measurements are always useful and welcome.
In the meantime, there are a lot of other people that have measured their own four Pi speakers too. So a search here or on the internet brings lots of response charts measured by other people.
Having so many other measurements gives independent confirmation in a sort of "crowd sourcing" way. It's useful to see so many different measurement systems and conditions showing agreement with what I've measured.
As for me and my measurement gear, I develop new designs using Smith & Larson equipment because it has a feature that lets me build a digital crossover using a Spice model. So I am able to tweak the values of the passive components in the Spice model to see the effects. This lets me dial in the position of the forward lobe. It uses an MLS signal for measurement.
I then use LMS outdoors for the measurements I publish. I drive with a specific drive signal and distance, one that provides equivalence to 1W/1M. It's usually two meters but sometimes can be as far as ten meters, especially for basshorns. I also measure on-axis and at various off-axis angles in ten degree increments.