Just intended to do a Quick Look through the posts. I am using the Kirk foot on the 4.5/6.3 & 70-200. There does seem to be a difference. Looking at the image in an earlier post of the Hajnar the foot seems to be extended back towards the camera body, leaving a pinch point between the foot and the camera body. Especially if you are using the Z9 with the built in grip. I don't know for sure since I don't use one. I would have gone with the RRS except that they were way late to the game I decided not to wait. One reason I like to go with RRS is that I use their ball heads with a lever clamp. Looking at RRS website under compatibility the lever clamp is only compatible with RRS plates. Although I have never had a problem between it and Kirk plates.