Yeah, those are some interesting docs. I might have to put those on the site.

Maybe there's another doc I haven't seen, but this is the only one about GG encoding that I know of:
http://nesdev.parodius.com/nesgg.txt

One thing to keep in mind is that GG codes work on the actual address in the ROM. So while the NES sees everything at $8000-$FFFF, the equivalent GG addresses are at $0000-$7FFF.