the trainer i learned on was an arf had a supertiger 61 on it and i had to put lead in the nose to balance. it had a bolt on wing. if i were to try making a sport aerobat i would take out dihedral have a bolt on wing and split the difference between 40 and 60 and get a 50. then the difference in weight is going to be about the weight of you battery so you can mount it where you need the balance. clip the wings acouple of bays and increase control throws a bit. its amazing what can be done with a trainer if you are kit building it. you can get it to do just about anything.