Duuuude... chillax!
its not a big deal...get yourself a roll of electricians rubber tape and a few scraps of sheet metal... wrap a few turns of rubber around the chain stay to prevent the frame from being scratched up then cut the sheet metal into a shim to fit between the mount and the chain stay... wrap a few turns of the rubber tape around the shim to hold it in place... the sheet metal will fill in the gap and the rubber will keep it in place.
see? no biggie.