I've seen a Model 3 at a couple of local EV events with an EZ Pass in a similar location, only it's mounted higher up, on the back of the screen. The owner told me it works fine that way. Your location makes it a little less eye-catching from outside the car than the one I've seen, but it's otherwise the same concept. One drawback for either variant has occurred to me, which is that this location makes the EZ Pass number extremely visible from outside the car. I haven't heard of anybody trying to hack into an EZ Pass account, but I could see it happening -- say, to request additional transponders to be added to your account, thus freeloading off of you. An easy fix, which might also help the aesthetics of it, would be to cover the transponder in a black plastic or cardboard box. You could cut up something like the black tray that some frozen meals use so that it fits closely around the transponder and then tape it in place around the transponder. Wrapping the transponder in black cardboard from a crafts store should work as well.