The Kaos isn't known for it's knife edge characteristics. Not because of the size of the rudder but because of the small side area. Notice that the rudder does a fine job of picking the nose up in knife edge but it still sinks. Just not enough lift.

If you want to modify it to improve knife edge you need side area. Maybe a long turtle deck and forward canopy like on the Ultra Sport.

I agree with Ed on the prop, I run my .46 AX and .46 SF with APC 10x6s and they sing. He's right about the CG too. Keep moving the CG back until your vertical dives are truly vertical. Then trim out the remaining coupling with mixing.

Rolls should be great and shouldn't need differential. Work the elevator a little and you should be able to do rolls in a straight line from horizon to horizon.

Dave