I use a Sachtler 18p with the heavy duty legs. With a cannon J20 and a wide angle zoom thru on the front you need the stability. Always been very happy with it.
I use the 500 with a Sachtler video 15 SB (speedbalance) and find it a tad too light (especially when telephoto or doing copy stand work).
I switch to an 18 for that stuff. But that's a monster to carry. For run N gun the 15SB is perfect with a 500 without any accessories (mattebox/monitor etc).
