On my own lead sheats I use the parentheses to indicate both passing and optional chords, but usually optional. Like, if i can fit them in comfortably, or, if I'm playing the song solo and it needs some filling-out, or I want to change the melody line or harmonics a bit for a different verse or chorus. For polychords and chords with altered bass notes, I use a slash (/).

And Penguin Egg, there ARE 5 and 7 string guitars. I've seen them. Don Ross plays a 7 string he had custom built. And then there's Linda Manzer's Pikasso, built for Pat Metheny.

There are no stupid guitar questions. But you can get stupid answers.