Cough cough. Here goes....
I have used the GME ground independent on a clamping bracket which is a great setup. rated at 6.5dB it gets good range and clarity and is easily up to the job of tracking 'traffic' with the truckies on Ch40.
However, as per your comments I hated the need to clamp etc and so I moved to a glass mount. I have always used RF Industries products as they are well known for ultra high quality (see
www.rfindustries.com.au ). I switched to the glass mount UHF aerial which looks identical to the older Whisper series RFI cellular aerials. It ahs two options for whips - one is a 1dB short whip for around town etc and a quick change 3dB gain for the highway or longer range.
The RFI aerial works well and with the 3dB whip is capable of the highway work I do. certainly not as good as the 6.5 GME though. The key with the glass mount is the coupler adjustment which must be done per the instructions provided.
For the record, the NSW Police use these RFI units on their cars for data and voice comms (although they use a different frequency).