Looking over it, the only thing that needs to be changed is the damage rating. Since it's an anti-fighter missile focused more on longer ranges, it still needs to maintain a similar degree of acceleration and maneuverability, otherwise it'll be crummy at its job. This means the payload is likely to be about the same, with the extra mass being devoted to propulsion.
Knock the DR and fragmentation range down to the same as the atrop, and it should be good to go.