As an added note: You will need to use the white plastic standoffs that came with the original mounting grommets. These insert through the middle of the grommet assembly and are critical to the mounting functionality.
I'm just finding time to mount my V4 drive now. At first I didn't believe it would fit on a V3 mount equipped plane, but then realized that Brenner solved the compatibility problem in a neat way: the V4 motor mount plate mounts to the backside of the "firewall". (the V3 motor mounted in front of the firewall)