Just had a newsletter from the local police offering free postcoding for bikes. The description states "Please note that the process will involve engraving the underside on the bike frame. We will then seal the engraving to protect it from the elements" Just a bit worried how safe this is on an aluminium frame...especially as it appears the actual engraving is to be done by the local bobbies, not a bike shop person... Has anybody else has it? Any frame problems? Does it look messy?