Hi
We use 6.5 at work so I downloaded the demo 7 version and tried the above out. It does work, but you need to make certain that nothing 'touches or overlaps' the floating boxes on the either side. I made 2 boxes left and right that were 1pixel wide on the Master Page and locked them.
If any of my other page elements touched or overlapped the two locked side boxes then that particular element would go awry and move all over the place. But it seemed to work ok other than that.
Wonder if 8 has the page centre ability...
Andy