I site in with a 2" black square. Put crosshairs in the lower right, like a carpenter's square, and sight deer rifles to hit the top right corner, ends up 2" high at 100yrds, and very easy to see where to make adjustments as needed.
Square size doesn't matter much when you are sighting on square corners, corners are just as small/precise on a 6" square as they are on a 1" square.
