MIKEI'm with Sam on the turntable. But you have to get the one GRS sells it's so much smoother than the home made ones. I made one from the directions from the air graver site. It worked but the magnablock is to heavy for it to spin smoothly. Just my experience, if you got a heavy block don't waste your time.
I personally didn't find much use for the GRS turntable attachment kit for the shelf. I use a magnablock it seems to big for that setup, but it probably would work better for the low profile or standard block.
Maybe Sam can elaborate on that.