Sorry for delay in seeing this, most of the TomTom units I have tried over the years have been attached to the Brodit Pro-Clip system by a small modification to the mount supplied with the device. In the case of the Start25 can the windscreen sucker be removed from the back of the TomTom, there are some pictures on the TomTom web site listed under accessories that suggest it can be seperated.
This is what I did to one of the Easy Port mounts a while ago, it might give you a few ideas, the Brodit Pro-Clip attaches above and below the air vent rather than directly to it, this provides for a very stable mounting solution, no screws are needed to install the kit:
First off you will need a Pro-Clip to suit your vehicle, there are loads to choose from, and the Brodit TomTom Ball which, in this case was salvaged from an x40 Brodit Mount, but a Brodit/ TomTom style ball is now available under the part number of
533091 directly from Brodit/ ProClip, here the Brodit "Ball" is attached to the Pro-Clip sat next to the standard Easy Port windscreen mount:
Look above the hinge line and you will see two small rubber plugs, these need to be removed (they simply flick out using your finger nails) to reveal two Philips head screws:
Remove the two screws and the mount comes apart very easily:
Place the old windscreen sucker part to one side and re-assemble the ring portion of the Easy-Port mount to the Brodit Ball by trapping the ball between the easy port ring and top cap, secure in to position using the two screws, these only need to be nipped up do not over tighten:
The Pro-Clip plus the Easy-Port secured in to my car (Ovlov V70), the Brodit Pro-Clip simply clips over the airvent securing to the structure either side of the vent to provide a solid mount for the navigation device, no holes are needed and if removed no traces of it being fitted are left in the car:
Finally, what does it look like with the device attached, if you want the device higher up rotate the entire mounting ring through 180 degrees and the device sits 75MM (3") higher (shown in the low position):
I route the power cables through the airvent which is fiddly to do but well worth the effort if you don't want cables all over the inside of the car - Mike