2 seconds isn't really enough time to do everything you need to do to get off a good shot most of the time. But I will assume you have that all figured out!
If you have to do the holdover thing then I would sight in at 400. That puts you
6 inches high at 100
9 inches high at 200
7 inches high at 300
-13.5 inches low at 500.
I would think if you could range some approximate distances before hand, it wouldn't be too hard to estimate range by memory and make a good shot.
More preferable to me would be using a reticle for holdover. I really don't like ballistic reticles but this would probably be one style where it would work really well. NF's velocity reticle seem ideal for this.