I didn't add any weight, I just installed the batteries behind the firewall, the fuel tank in the stock position and used an Aluminum spinner.
It ended up just a bit tail heavy, but nothing to worry about.
I want to make it lighter still, by changing the metal gears in the DS8411 servos to plastic, this should balance it a little bit better.
I had the Saito in a Staudacher and was supposed to install it in a U-Can-Do, but this excelleron got in the way and stole the engine.
I am very happy with it, as my other option was a YS140, but did not want to go to that extreme.

A friend (grillo) is installing a YS 120 in his, and it's gonna be a rocket.

Gabriel