Put mine inside the car near roadtax. Just stick with tiny scotch tape.

Did the same to my friends and family. 7 cars, all 0 issue.

Only thing common is all of them have ceramic tint. Although they are different brands and price range, key is pure ceramic make sure not metallic nor metallic/ceramic hybrid.

Metallic tint even if you stick rfid outside the windscreen also will cause interference because the aluminum/copper etc particles will reflect RF energy. The guide said at least 5cm from any metal, that's the only rule need to adhere strictly.