Has anyone used the varizoom shoulder brace and been satisfied with it? Would this one or the SP7 be preferable for some degree of comfort and stability?

I use the VariZoom VZ-LSP and I like it a lot. It's just barely enough for the XL1. Basically the VZ-LSP is a huge improvement over a competing product, the Mighty Wondercam. The Wondercam is a cheap knock-off of a Peter Lisand design. The VariZoom VZ-LSP, however, *is* a Peter Lisand design.

The VariZoom Media Pro (formerly the SP7) is perfect for the XL1, and a bit larger and more expensive. Both of these have been discussed here before, try a search on the names. See the SP7 write-up on the Watchdog. Hope this helps,