Sticky pads have an anoying habit of falling off at the most inconvenient moment. Not something I would recomend, especially as you will be stressing the pad every time you take the phone out or put it back in the cradle. Which just loosens the pad's grip a little every time.
Best bet is to find/make a bracket like the one Orange fitted to my car. It is basically just an L shaped bit of metal that the installer screwed to the side of the radio. He popped the radio out, attached the bracket then slid it back in. So you end up with a mounting plate to attach the cradle and no holes in the dash.
I did buy a car kit a few years ago that had a plastic L bracket that would have done a similar job. All it needs is enough gap down the side of the radio to slide it back in place with the bracket attached.
Not sure if you can get the brackets anywhere though. Orange fitted mine for free using a voucher that was in the car kit box. Though that might be because it is a company phone - it was the full Nokia hands free kit as well which might make a difference.