I used to work for shannons, i consider myself fairly acquainted with the policy. I'm telling you they will not/can not, deny a claim because of a modification unless they can prove beyond doubt that the modification in question caused the accident. Best of luck with that.

I've relayed to you my advice based on my personal experiences, as you requested in the OP. I've been playing with cars, yellow stickers and the rest of it for over a decade now, use it or dont, as I said its your prerogative.