I use pull pull for mainly two reasons. control is always pull and I can save 12 grams or better from a tail heavy plane. For reference the horn connection holes should be at the center of the hinge. IMHO that is a given unless you are trying for mechanical differencial - not a place I go. Pull pull is geometery and every thing needs to be centered and the same or you will get slack or worst extra tension. How much and which one depends on where the setup is off from perfect. I never achieve perfect and usually have just a bit of slack at full deflection. I try very hard to align my horns with hinges.

Carl