I have a Petroff matte box I bought several years ago with an eye toward one day owning a RED camera. I never used it, just left it in the box until the last couple of weeks, when I've been completing the rigging for my new Epic. The Petroff works as either a clip on or with (in this case) 19mm rods via a bridge support bracket (which I prefer when using my longer lenses because I'm letting the mattebox support double as lens support.) I'm using the x 19mm bridgeplate with riser to bring the Epic to industry standard 19mm compatibility.
The hitch is that the support bracket for the matte box snags on the front of my Arri dovetail plate if I try to dismount the camera from the back end of the plate, and, conversely, it won't even allow me to mount the camera from the back end of the plate because the bracket is clearly protruding below the bottom of the bridgeplate itself. I tried reversing the bracket (turning it upside down), but it snags in either configuration. Since I'm using a safety dovetail with hard stops on the front and a spring loaded saftey catch on the back, it's necessary to mount the camera from the rear of the plate. I've considered but rejected (for reasons I won't go into) the feasibility of reversing the dovetail plate on the tripod so as to put the spring loaded safety catch on the front side and the hard stops on the rear. While this would allow me to mount the camera in reverse, backing it in from the front of the plate and thus bypassing the possibility of the matte box support bracket coming in contact with the dovetail plate, it causes other problems with my configuration that I don't want to have to deal with.
My question is whether this is a normal limitation of matte boxes used in 19mm studio configurations, whether the Petroff bracket is just poorly designed in not allowing the proper clearance, or perhaps whether the WC baseplate is at fault for not including a thick enough base below the level of the rods holes so that the rods themselves sit up a bit higher vis-a-vis the level of the dovetail. For the life of me, I don't know how the support bracket could be much shorter profile than it already is, so I'm inclined to think the problem is more due to an inadequate amount of thickness on the WC baseplate below the level of the rods holes.
I went with 19mm rods instead of 15 because I like the idea of being able to use one length of rod and slide it back through the baseplate to fit a number of different length lenses, something you can't do with 15mm rods because they run into the camera front. But I'm thinking now I will either have to deal with the inconvenience of removing rods everytime I want to move the camera from the dovetail plate or else go with the 15mm rods that sit up higher and won't therefore interfere with sliding the camera fore and aft on the dovetail. Or maybe go with a different baseplate with a thicker bottom.