TCR, What you describe is normal. Flaps do two things. At low deflection angles (roughly less than 30 degrees) they increase lift, after that the increas drag. From a straight and level flight if you lower the flaps the full way you have a huge increase in lift, and the plane balloons upward. In a full scale 182 you milk the flaps down, 10 deg on downwind, 20 through the turn to base 30 through the turn to final and the rest of them if you need to steepen the decent angle. Some radios will mix in down elevator as you add flaps. Otherwise just hold what ever down elevator you need to hold to keep the nose from climbing.

HTH
Tom