Thanks guys. Your input is much appreciated.

Unless new insights arise, I will proceed with interpreting this positioning as being a position requirement for the cylinder at Point G's location only (the point G itself not having anything to do with being toleranced with a sperical tolerance zone, halting translation of the cylinder along the 18 degree axis, etc.). Point G merely designates a point where the Basic axis exists, and at 18 degrees. This means the cylinder may translate for infinity up and down the axis, as long as the cylinder's axis does not violate the .010" (plus bonus tolerance) cylindrical tolerance zone existing around the center of the 18 degree Basic Axis.

Using a cmm, people had been constructing a pierce point out of the intersection of the cylinder's axis with the Flange's face, and testing its distance from Point G's location using a spherical tolerance zone.

Instead, we'll merely translate our origin to Point G, and take several hits around the inside of the Flange's hole to see if the hole's center violates the diametrical tolerance zone at that point. I should also do the same with the back of the cylinder (2nd flange) in order to prove that this cylinder as a whole does not violate the tolerance zone.

Thanks again, guys!