tony robbins claimed he got huge off of Mentzer's static contraction training, did you give that training style a whirl?
I have a book on static contraction in my bodybuilding library, and I've tinkered with it but the two programs I primarily built the 23" Guns with were Arnold's Encyclopedia and Ironman's 10 Week Size Surge. Also an honorable mention goes to Brutally Huge. I tend to cycle routines and I've been on a bunch of them.