I don't know if you've tackled this project already or have gone in a different direction, but I just found a 6" pedestal extension (8" in diameter, I believe) here:
Just ordered it, so I'll let you know how it works out!
Sorry, link was deleted. I ordered it from unfinishedfurnitureexpo dot com. Just do a search for "pedestal extension" and you'll see it, part WWt7P.