I have a saito 180 in mine about the same weight as the os 160. I have my servos under the wing and my battery is right behind the firewall. No added weight but I did have to put the battery that far forward for balance. I would think if you put the servos in the tail you would either have to add weight or go with a heavier engine. Make sure to set the tail at 0 degree incidence with the wing. Mine was off and took some effort to fix before gluing but well worth it. Its a great plane. Although it casn be hard to see in the air some days. But that is only when its more than about 15 feet off the deck! Happy flying