D'oh. VZ58 woes continue. It chronos at or around the stated 320fps...without hop. But in order to get enough hop to lift .28s, it increases to the equivalent of 365-370. D'oh.
Prompted me to give it bit more of a google as hop-up increasing fps was v curious. Seems there is a threshold for it increasing it, although you getting 40fps off it suggests it's bit over-volumed too (not to a point where it'll cause issues firing 0.2 as intended)