Site BBs in your mag, 0.3g or higher - I'd actually say 0.4g+ these days. If a site can't afford that, they've got bigger problems.
And to veer dangerously close to getting back on topic, using a single weight of site BBs also allows dinosaurs to keep thinking in fps, as they'll only have three numbers to deal with: AEG, DMR, sniper.
It just shouldn't be 0.2g BBs, and 350 / 400-something / 500, for the obvious reason that these numbers and energy levels won't represent what will actually be produced on the field when everyone switches to 0.28g - 0.46g BBs.
There are exceptions, like CQB sites which only allow up to (e.g.) 0.25g, when the Joule creep over 0.2g isn't likely to be massive. But for woodland, in general, quoting in 0.2g fps figures is risibly old fashioned.
Because at the end of the day (well, at the start of it), they don't really mean (e.g.) 350fps, they mean (e.g.) 1.13J, and all of their numbers for other BB masses are derived by converting 350fps x 0.2g to Joules, and then back again. So why not skip the pointless first step, and just specify and think in terms of Joules in the first place?