Hey used the Arkon mount this weekend w\ the Pharos, I did not lose the signal at all, lots of buildings etc. no problem. The headphone jack did not fit, I went to a couple of electronics stores to find a shorter jack but they(sales persons) said that it is a standard part so I will probably not be able to find one that is shorter. I am going to use the mount with out the speaker for the gps I just turn the volume up on the Axim,(I have a deisel car) and I am not having any trouble hearing voice prompts. The Pharos people said that I could send the mount back even with the shaved jack but I am too lazy to wait for another.
I actually like how it is working in the car and I have the dash mount so that it does not block the view of the road. Atlanta traffic is a little crazy! Let me know if you find anything to modify the jack. Arkon was really great about the whole thing.