I have the CA-2x4SR mounted on my Jeep. It's on a corner mount just above the taillight. My SWR in GMRS is less than ideal, but 2m is near perfect. I'm looking to try out the Laird B4505CNS next for GMRS. I don't think there is a flat enough ground plane to help out my GMRS numbers.
SWR:
462 - 2.03
467 - 1.8
146 - 1.08