Yea, that 91 in the nose is a lot of weight. I've had a YS63 and a Saito 72 in mine, both lighter than the Saito 91 and had to put the battery at the trailing edge to get to 4 1/2 and add lead to get to 5. 4 3/4 seems to be the comfort point for mine. I can hold the nose up and it only takes very slight down in inverted flight. A real fast servo on the rudder also helps. But it's still a hard plane to control because of coupling. But it will now do stuff it wouldn't even start to do when I had the CG between 3 3/4 and 4 1/2. I also put a 5 cell pack in to get the servo speed up. A much better flier than me and a computer wiz could probably make this thing work.