As an aircraft sheetmetal mechanic, I can vouch for the Acetone as I use it every day. Works like a champ.
I would also consider using a phenolic or plastic scraper. With the pinstripes being over the clear-coat, you should have minimal (if any) possible scratching. Nothing that won't be taken care of during your next wash/wax, which I would recommend doing within a reasonable time of having used the Acetone/scraper.