In the instructions that came with my Superlift kit, that i used when I put my Superlift kit on, they tell you in plain English to do up to a 1" tbar crank to gain up to 5" out of the kit.

I don't know why you got the only kit that was 6", but the ones they are selling now are 4" and with a 1" tbar crank up to 5".