The zacuto is nice, but I found it uncomfortable on my shoulder and returned the rig. It's also a little pricey I thought. Check out the varizoom rigs. It's quite a bit more affordable and some models have a cool spring loaded rod that slips into a belt assembly that I find really helps me stay steady on longer shots. It takes all the weight off of your handgrips, it's nice.
The zacuto z finder is by far the best focus lupe I have found. The mounting ring is flimsy though, but it works very well