Re: Frank Zappa solo theory?
Read his autobiography (The Real Frank Zappa Book), if you haven't already. He doesn't go into many technical aspects of his playing, but he does talk about his perspective on solo's, his own and other peoples. Plus it is a great book, one of my favorites; full of all of Frank's witty charm and crazy intelligence.
P.s. I've been told I have a very frank like style when I try to (if I'm jamming over Black Napkins or something). And I've been told by people that they can hear some Frank in my playing when I'm not even trying to play like him. It wasn't necessarily something I did on purpose, I think it just came from loving his playing and listening to it a ton. And of course, I take it as a huge compliment!