I have 2 of these caps one with the Moki and the other has an O.S 1.60. Neither one needed any extra weight to balance, the Moki and a 6v. battery mounted on the tank did it for one and for the other I mounted my throttle servo up on the backside of the firewall and mounted the battery on top of the tank I ran dual elevator servo's in both and on the one with the 1.60 I just moved the rudder servo forward a few inches, that took care of the balance. You don't have to add a bunch of weight for balance with the 1.60 just move things around a bit .