Since your seat is all the way back and we must assume that your steering column is not adjustable or telescoping, any modification you do to the rails will void any insurance claim in case of accidental death to a driver. Contact the dealer for a set of OEM rails for tall people, that is the only legal option I can think of. Are you sure the seat is moving all the way back? Have you pulled up the carpet to see if there is another set of mount holes in the floor?