The Toll Roads (SoCal) advised me that Tesla windshields block the regular transponder, so I have to use the external. I ordered the external and it got here. It's bulky and, despite my initial impression, goes on the front plate bracket, not the back. Good thing, too, because that's where the backup camera is. Some people posted photos that show it mounted. They claim it looks cool, I would go with "inoffensive". It does appear that the transponder is screw-on, and the front plate holder is a glue-on. Is that correct? How have others gone about it? Buy a third party plate holder that screws on? Drill holes in the Model 3? (Sacrilege!) Can the transponder be mounted to the Tesla's own bracket somehow? Also, it appears that the Toll Roads people are wrong about the windshield, that their info pertains to S, but not to 3. True? Did you mount your transponder on the windshield? If so, top or bottom corner? Can we see photos? Sounds ugly, but one gets used to anything, even carpool stickers. Did you place the transponder inside the car somewhere? Not what The Toll Roads requires, but I seem to have gotten away with it for 10 years with my MBZ SUV and did not notice any fines or overcharges. Sometimes it beeps, sometimes it does not. The license plate is key. They told me I can be charged by license plate anywhere but 91. I don't go on 91 all that often. How did you go about resolving the transponder conundrum for yourself?