I can remember a few times I've logged in to 90-120 people in flight, with bardar only showing enough for 30 people or less assuming no NOE. As a percentage overall GVing might be not that much higher, but has more of an effect off peak?
I'm currently looking into that thing, with the limited tools I have at hand.
Unfortunately, I can't really track time in modes at smaller intervals than once per (completed) tour. But I am able to track the killstats for planes and GV, and they show that the GV game (unlike plane activity) is often going even to absolute zero at offpeak.
('activity' data from last few days. Plane kills&deaths are blue, GV kills&deaths are red.Maps during that time were ndisles, baltic, ozkansas, sfma, craterma. Time is CEST. Sampling rate in this chart =1h)
It needs a higher number of players to get the GV game going, as is apparent every time CraterMa is up. At offpeak tank crater is often totally deserted, only at later hours the spark ignites the ground fire, so to say.
I have also scanned the map for flashing towns, which would indicate (milking) GV activity there, but I couldn't see much of it either.
So far I'd say GV activity at offpeak ain't really increased, at least not significantly