This a reply I got from them today on there glass mount. I'm also considering the one you've got..

Thanks for the reply


Thanks for your inquiry about our On-Glass XM antenna. We actually offer two On-Glass models, one long and one short. Generally, the longer XM8000F is used on large vehicles like mini-vans, big SUVs, pick-ups, etc. that need to be mounted on side glass. The top of the antenna mast needs to be above the roof line of the vehicle for best performance. I think, however, the PT Cruiser could get by with the shorter XM81000F. The XM81000F also will likely look better on your vehicle. To purchase one try www.crutchfield.com

Good luck and enjoy your XM!!

Mike Uxa
National Sales Manager - Consumer Products
Antenna Specialists