A guy at a sign shop told me that magnets needed to be bigger than 11x17 or they would blow off going down the road. Vistaprint just came out with magnets but the largest size is 11x17. I'd much rather get a cheaper one from vistaprint than spend over 100.00 for one at a sign shop. Does anyone have an 11x17 sign and if so, do you have any trouble with it??? Any better places than Vistaprint to order from?