I don' t know how practical this is, but I just turned this into a basic math problem. As an engineer, I always have to draw out a diagram to help figure these things out. So on the left side of the diagram we have a single point (the eye). 30" to the right there is an obstruction (pin) of .03" . We' ll assume you' re shooting horizontal to the ground to simplify things. Since you' re pin is centered perfectly we' ll draw half of the obstruction above the horizontal line and half below. Now you have a triangle shown from the eye to the top of the pin, down to the horizontal line, and back to the eye. Now, since you can' t see through the pin, we' ll extend that sloping line from the eye to the top of the pin, to the target 1018" (30 yards) away.

Basically, it works out to a simple geometry problem. According to this method, a .03 pin, held 30" from your eye, will cover an area of 1.1" at 30 yards.