"To summarize, if I am basing a song on D mix, should I just keep working at it until I find good sounding IV or V sounds by experimenting with inversions, or is it common to modulate the whole fretboard to shift into F or G mix in order to create that "shift" (like when you change from a verse to a chorus or bridge.)"
You should probably go ahead and experiment with changing keys. It's something I have been experimenting with lately too. It sounds like you know an awful lot when it comes to changes within the same key. I started getting into this more when I fugured out how to play the Beatles song "Something." There are a couple of key changes in that song, and it got me thinking about how to apply those kind of things to my own stuff.
You can check out my cover version of Something here if you want:
Re: Advanced modal question
"To summarize, if I am basing a song on D mix, should I just keep working at it until I find good sounding IV or V sounds by experimenting with inversions, or is it common to modulate the whole fretboard to shift into F or G mix in order to create that "shift" (like when you change from a verse to a chorus or bridge.)"
You should probably go ahead and experiment with changing keys. It's something I have been experimenting with lately too. It sounds like you know an awful lot when it comes to changes within the same key. I started getting into this more when I fugured out how to play the Beatles song "Something." There are a couple of key changes in that song, and it got me thinking about how to apply those kind of things to my own stuff.
You can check out my cover version of Something here if you want:
http://home.earthlink.net/~guitarjoe/Albert_Salazar_and_David_Heise_Something_Beatles_cover.mp3