Sirui L-10 monopod tilt head, similar in design to RRS, but I have not done direct comparison. I do not have any issues with a 1dIII/gripped 5d with 70-200 f/2.8/400 f/5.6. It is AS and have not issues with RRS, photoclam, and a Kirk plates
B&H and Adorama carry them, but do not have them out for you to play with.
EDITED: One negative that the Hejnar addresses is that the Sirui is stuck in only 1 orientation, while the Hejnar and the RSS can be rotated so you can use an L plate, and simple plate, or a lens foot and still be able to "pan" up and down. With the Sirui, if you use a L plate, you are stuck "panning" left and right or adding a nodal slide to change the orientation of the AS plate by 90 degrees to fit properly. Since I only use the lens foot with an AS plate attached for the monopod head and rotate using the collar, not an issue for me.