Hi OnTheEdge

The pop-up sound like your using too much elevator and maybe too little rudder. Play with your timing then see what happens.
As for your pitch coupling with rudder, I ask of your; are you unintentionally pulsing your throttle when you move the rudder stick? That would indicate there is too much down thrust. Also makes me wonder what you are flying? few scale aerobats have pitch coupling with the rudder because engineers like myself design this out of these type of aircraft. Roll coupling is harder to get rid if without damaging other aerobatic qualities I.E. Roll coupling with the rudder is much more common. And as for Mixing, I don't use it but if your coupling is in fact aerodynamic you could mix it out or you the pilot could compensate for it.

I hope I could help you a little, Happy Flying