A typical Persian should weigh between 7-12 lbs depending on bone structure. Your cat is within those limits so I definitely wouldn't regard him as being overweight yet.
My cats, Chinchilla Persians, which are a Persian breed, are smaller and lighter boned than an average Persian but that is typical of the breed, and although fed mainly on JWB and Hills dry foods they dont seem to put much weight on. I would be very happy if they did as it can be a problem when competing against the larger and heavier Persians.
