I've played a fair bit of CQB and my local site initially tested only on 0.2's, but saw the error of their ways and now you test on the setup you plan to use. They'll pop a few BBs out of your mag to check the weight, they even have more than one chrono so no-one needs to faff about changing the BB weight settings. This leads to an efficient chrono and eliminates any joule creep issues as the game setup is the one that is measured rather than an inaccurate one set by the sites rules (which is a bit of an own goal tbh).
I'm not a fan of HPA because a gunbilical cord isn't my thing, but from what I can make out the issues with HPA stem from either Joule creep due to testing inadequacies (see how my local site started out), or the operator willfully abusing the system and not being caught. In an ideal world everyone would understand joule creep and understand that if a site were testing on 0.2's then they would need to be under the limit if they were planning on using 0.3's. In an ideal world our honour system would enough to stop a post-chrono regulator tweak even being considered. But it's not an ideal world is it.
At the end of the day, it's your site, your rules. Stoke's miles away from me and I'll probably never visit; I'm sharing my experiences and some thoughts on chrono and levelling the field. Do what you like, but I find simple rules are easier to understand, follow and police - 1.14j on the ammo you're using is all you need to say.
Also, I can't believe no-one's mentioned shotguns in four pages! Are you really doing survival horror properly if you don't have a short-barreled shottie? 😁
All the best with the Seige though 👍