Gridmove is a fabulous little utility for those of us with lots of screen real estate to manage. Having become somewhat addicted to Gridmove, I was sore to see that the default .grid files didn't support my new third monitor.
Fortunately, this was easier to fix than I thought. If you're interested in custom grids, skip the help file - it's loaded with terminology. Just open up an existing .grid file with notepad, you'll see how it hangs together pretty fast.
Here's the grid. All I did was expand it to three monitors. Eventually I might delete the elements I don't use, but it works well as-is.