Second on the heat and solvent. I recommend a heat gun. Hairdryers never generated enough heat for me to get registration numbers off, let alone factory installed decals. I've even gone as far as using a propane torch - dangerous and tricky on gel coat - not so much a problem on painted aluminum. I would also recomend generous use of something like Goo Gone. Get a corner of that sticker/decal up and spray the underside with the solvent and work it off a bit at a time with a plastic scraper (metal and razors tend to cut gel coat and paint too easily!). Patience and persistence pay off on this one.
