I suggest if the cab wasn't delivering for you then you should replace the damaged cone with one original and sell. Then get a better suited cab. Cab designs are very complex especially dual cone ported varieties. If you replace one of both cones with anything other than a driver the original design parameters either you will kill the remaining cone or it will sounds crap or both. Retuning the cab would require modeling from Theile Small parameters of the drivers. If they are matched it really hard, if they are different, it gets propper complicated, if one driver is old and its perfromance has drifted form the design parameters due to changes in its physical elasticity and hence frequency responce change...............well you get the drift. Fix it properly with a matching cone , sell at a fair price and get the one you need.