My two cents: Put your pitch shifter after the amp, before the cabinet. Putting it before the amp means you're running the harmonized note into distortion, which has a totally different sound from harmonizing a distorted signal. Imagine the difference between playing a power chord into an amp, and recording it as two separate notes. You'll get much more clarity with the pitch shifter after the amp (or splitting it to run stereo). If you are running it after the amp, put it before the cabinet. The cabinet model has a resonance peak (I think), and the pitch shift will move that as well if it comes after the cab, which can create a slightly less "realistic" sound.
More importantly, what about it do you find lacking (or too excessive)? That's the best way to begin thinking about what you need to do to improve it. And if the answer is nothing, but you don't trust your ears, then you need to let other people hear what it is you've done in order to identify any potential improvements. When it comes to tone, demonstration is far more effective than description.
Also: excellent info on the
wiki