Congrats with your maiden. Even though it might have been stressful. The 2 degrees incidence of the stab is most likely because:
The Decathlon is designed to be an aerobatic airplane, therefore it uses a semi-symetrical main wing airfoil. The bottom camber is about half as thick as the upper side of the wings, depending on the airfoils name and variety. Because of this thickness difference it actually has more drag over the wing than under and without your positive incidence to lift the tail a bit, the aircraft would raise its nose continously.

If the aircraft is climbing out of dives, it does not have to be tail heavy because of this tail incidence versus main wing thing. If it balanced perfectly at the given example of CG, then I think your engine needs a little bit more downthrust.
I was using about 3 degrees down, and over 2 right wiht my 61 4-stroke. Might even become more with my 80. It seems that most people don't think to much about this. But it really is important. To o little right thrust makes the plane slip to the left, making takeoffs critical because of more lift on the left wing as an indirect result of this, causing the plane to tipstall to the right!
Too little down-thrust makes people think "****, it's tail heavy". And in an engine out situation, the nose will then be waaay to heavy because of removed weight and this again causes much shorter gliding distance. OK! IT IS MODEL AIRPLANES! But shorter gliding distance=MOST PROBABLY THE 4 OR 5 FEET YOU CAME SHORT OF A SAFE EMERGENCY LANDING! Or you JUST MISSED the top of that tree because the plane came down too fast...

Some things to consider. It's just things I have learned during my modeling career. Hope you can get something out of it.
Anyone who disagrees surely have some other cool ideas of fixing these tendencies.