From reading some of the posts here it is my understanding that the H9 Aresti isn't that great in knife edge flight and that the rudder in general is a bit weak. I am about to start construction on mine and would appreciate advice on enlarging the rudder.
About how much should it be enlarged ? Also, is there much coupling in knife edge with the rudder and if so in what respect ? Would it be best to change the shape of the rudder a bit when enlarging it, ie., by increasing the cord at the bottom or top of the rudder ?
I am also considering taking out a bit of the dihedral. Opinions ?

Thanks,
Dave

I dunno know, mine knife edges just fine.

The Aresti does not do that great a KE but its not lousy either. Take your CG back a bit, mine was with a Saito 72 and I had about 2 oz of lead in the tail and I could have taken the CG further back without the plane being twitchy. My WM Super Chipmunk does a much better KE than the Aresti. There is no need to have a larger rudder.