Many trainers do come with dihedral in the wing, if that's what you are referring to. That said, I can't say what you will find with the latest foam planes but, with a wood ARF for kit, there will be some. A plane with ailerons will perform best with a low amount of dihedral as anything greater will have the wings fighting the ailerons. It really depends on the plane as to whether it has ailerons or not. I'm currently building a pair of Sig Kadet Jrs from plans. This plane is designed with a 48" wingspan with 2" of dihedral due to it's 3 channel design. I'm building mine with between no dihedral and .5" so that ailerons will be effective on both. Had I left the wings with the designed dihedral, ailerons would have been a waste of time