may be of no help this but only you can decide. I have tom tom on phone, not releven,but the clamp i used to hold the phone may be tho, 15 quid from halfords it had a "clamp" for the phone which was removable and looked easy to modify(for your tomtom). And on the other end a sucker for glass BUT it also had plastic puck to fix, in my case, to the under side of the dash bit that sticks out over the clocks and info display. You can then bend the flexible arm to hold your device so it sits right next to the info display. Its not in the screen area blocking your view of oncoming bikes, is not reflected in the windscreen to distract you and is as out of the sun as its possible to get. You dont have to reach forward out of the chair to programe it, while ducking the run visor and its just above the lighter socket so no cable along the dash. Only problem, since i moved the puck a bit to a slightly better location, is on hot days the bloody thing keeps falling off and hiding under the pedals. Cant find sticky pads as good as the originals that will take the heat in a hot car.
Hope helps.