400 + here in Australia. I THINK the long lag times have an effect wrt field ack, but cannot be absolutely certain.
I've seen guys with low, low ping times strafe fields in ways I would never attempt. In fact, most of my ack deaths come AFTER the particular ack has been killed on my FE.
But for air-to-air, 400 or so is no problem, so long as I remember to add about 60 degrees to my opponent's angles.
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When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things.
Chapter 13, verse 11