I just flipped open Larger than Life 2nd ed which I know has sectional movement, and it doesn't have Fast Move in it at all...
How it handles it, you can move around your own unoccupied section all you want. You can move into an occupied section up to 4" then you have to stop. When you're in an occupied section, you can only move 8" on a turn. I could see just adding normal fast move and being able to move 16" in an occupied section (or out of an occupied section), or you could use it to move 8" into an occupied section (or maybe 6" so you don't get the COMPLETE drop on the enemy).
I dunno. Give it a try and let us know!