I just found this old thread and couldn't resist adding to it. Here is the nifty little Olympia (by Brother) that I inherited from my wife. I think it must have made from a hollowed out anvil, and then lead weights added for ballast. It is a nifty little stitcher though.
When I have to use two layers of silnylon, then I move up to this one:
And for three layers, this mo-sheene can definitely inject thread wherever I want it!