I live in the Chicagoland area and have XM now, I had Sirius previously. I have read multiple times at multiple sites that installing the antenna inside of the vehicle is not the most optimal place and to top it off you are obstructing the view of the satellite with the coating on the windshield as you described. I know depending on the make/model receiver you have they recommend installing the antenna as close to the radio antenna as possible. I currently have mine mounted on the roof just right of center above the windshield as that is where my vehicle radio antenna is mounted on the glass. I used to have the mag mounted antenna sitting on the dash of my Expedition when I had it and would occasionally lose signal. Once I mounted the antenna externally I never had a problem. The only spot you can see the antenna wire is the little portion(1/2in to 1in) that runs on the roof to the antenna. Personally I would have them mount it externally.