I have the the US 60 w/ OS 91 fx, i'm told it weighs the same as the 61. I have an 1100 mah nimh in the tail as far back as I could plus about 3 ounces of lead. Originally plane had no lead, flew fine and great with the CG where the book said it should be. People at the club said that the plane is capable of hovering and basic 3D manuvers and to achieve this add lead to the tail until you just need the littlest amount of imput to fly the plane level while inverted. Plane does hover now, but needs a pump to do it b/c it will start to sag about 5 seconds into the hover. This is primarly b/c I build the tank on the CG. All servo placement is where Horizon reccomends. I have seen people at the field with this place with the reccomended saito 100 and they had both tail servos and the battery in the back of the plane. Don't forget though that it's always better to be noise heavy then tail heavy.