Bob, when it comes to an aerobatic airplane the dihedral will affect two things. A yaw/roll couple and a pitch/tuck in knife edge. These are things that are associated with both having too little dihedral or not enough. Not knowing which plans you are building from it is difficult to say where to go concerning this matter. The difference really boils down to where the horizontal stab is placed on the fuselage. If it is in the scale location then I would go with the plans dihedral. If the stab has been lowered ( very common on most large aerobatic models ) like the pictured H9 Sukhoi then I would suggest making the top of the wing perfectly flat and the dihedral effect is created by the taper of the wing thickness root to tip. Even if your stab is in the scale location and you want better flying performance at the cost of scale appearance you may want to consider the modification. Hope this answers your question.