swaybar drop brackets

I"m going to make some swaybar drop brackets and I'm wondering if there is a formula for how much drop for a given amount of lift. Ex. I'm doing 2.5" of lift, do I need to drop them 2.5 inches? I know RE makes brackets that they sell with their lifts but no info on how much. Thanks for the help!!
ASAT

my drop brackets from a 4" trailmaster lift were 4". however, if you have adjustable discos like JKS you have a little more play. I took my drop brackets off when i installed my JKS discos and now have the swaybar mounted to the unibody again. Keep in mind when making the drop brackets that they need to be on an angle, that is 2.5" down along the Y axis not 2.5" down perpindicular to the unibody