I'm not sure what a TTN6 is - TomTom? Usually they have some kind of stickiness algorithm for when you go under bridges or into tunnels - it assumes you stick to the nearest road until you are about 10 meters out at least (My navman GPS/router does something like this - it was fun on a section where I was ON the PA Turnpike and it insisted I was on a side road). The nav software tends not to trust the GPS, or at least isn't good enough to distinguish Dilution of Precision, or even number of satellites, or DGPS via WAAS or EGNOS. The point displayed on the map even at high zoom (like my Zmapper for the zaurus, now working on the nokia) is often right on the line (well within 3 meters). But another problem might be the maps aren't always accurate. US14 has a new section (Janesville to Waseca MN) that still isn't on many online maps. So the problem might be an attempt to compensate if the map is off (or traffic is on the shoulder or across as in an construction zone).

On the topic of mounts, since I have an n810, its AMPS mount, and a DockNRock (amp+dual speaker handlebar clamp) on my motorcycle, I plan on mounting it there. I already checked it would fit. Now if the ice would just go away . I'm using an AMPS panavise mount I mentioned in accessories in my car.

However my GPS and my EVDO system might go elsewhere. The above image was from a KR1 router in a drybox I have attached to my sissy bar. The velocity data is live (series of KMLs), but the above was post-processed. I embed the datastream (not OBD2, but I've decoded enough of the traffic to know where the RPM, gear, etc is) within XML comments within the KMLs, so you have a GPS location every 200 mS, followed by records with system milliseconds and the j1850 traffic in hex which you can see if you examine the above telemetry file. (I used to carry an iPod, but won't need that with the Nokia).

Note that KR1 is a mips machine with far less power than the n810. It was just convenient since it ran linux, had two serial ports (hidden), and I could hack the firmware to add GPS.