For those of you with EoTech's on flat-top 16 inch uppers:

I'm familiar with what one can see and hit with a 4x scope with a cross-hair recticle on an AR. For example, hitting metallic animal silhouette targets out at 300, 400, and 500 yards.

What about those of you with an EoTech 512 - what is the smallest size target can you effectively see that you can hit at say 100, 200, 250 yards? Obviously large targets - but how small can you go? Aslo, do you sight your 512's so that the dot is positioned just below the target, or do you sight it to cover the target?