Negative in the top wing compared to the bottom is best for low speed stability. With this setup, the bottom wing will stall first because it will always have a higher angle of attack whenever the model is upright. With the bottom wing stalled and the top wing still flying, the fuse will act like a pendulum hanging from the top wing.

As far as aerobatics, the same setup works very well.

If you set the top wing positive compared to the bottom wing, the model will experience increased drag and will not fly as smoothly.

Been there, done that.

The best thing to do is follow the plans. That is how the model was designed and tested. The kit manuf knows what to expect with the model setup this way. Unless you are willing to experiment and possibly change the top wing after you have flown the model a few times, I wouldn't deviate from the plans on wing or tail incidence angles.

John

John