Thats a 2:3 ratio then like mine. Tail seems to be about 1/2 the disc size
This 14" disc mini marble cant have 30" length surely, thats a tail greater then disc size.
Im new to keeping rays as i only had mine a year so i have no idea if a tail length greater then disc size is possible from a mini marble. Ill post a pic later, think it could be a cross ?