Yes the F2.8L comes with the tripod mount ring.
The dovetail bar is a great option for mounting the camera Doug
I'd like to eventually get the 1.4x teleconverter to go with the 70-200, as Doug mentioned it only drops it by one f-stop, I believe the 2x version reduces the effective aperture by 2 stops.
David recently revealed to me that he has a Tamron F2.8 with a fixed focal length of 300mm, might put the Canon back into the camera bag for the next imaging session.