Bruno,

I've got a similar problem, but not quite so severe. Are you using any ail differential? I found a lot of adverse yaw in the original setup and programed in about 30% differential which removed the condition. I also increased the ail throw substantially to improve the roll rate. If you are going to seriously race at high speed the slow roll rate is probably apporpriate, but most of us just want to have fun. The plane still required a slight offset for level flight, but its only a minor annoyance. I also moved the CG forward 1/4" to reduce the snaps.

Good luck