Manfrotto has made the only easy available head for monopod for years, but now RRS came with a nice-looking piece of equipment that I liked to try on my Canon 300/2.8L IS. The package includes one MH-01 monopod head, one B2-Pro II screw-knob style quick-release clamp, and one 1/4"-20 flat head screw. I've mounted it on a realtively small and lightweight Carbon tripod, and with a swirl-base to be able to turn the whole thing.
Originally it was fitted same way for head knob and the clamp. I turned the clamp 180 degrees to get it away from my hands when operating the main knob.
To secure the camera from NOT falling of the clamp I invested in the original RSS base plate B61: Lens for Canon 300mm f2.8L-IS. This plate has safety screws preventing the equipment sliding of the head, and it works!
Conclusion: Very nice made and locks the 300mm easily! Recommended!
Oystercatcher with this combination attached. 300+1.4x = 420 mm