That is a characteristic (and a preferred one) of most flat bottom trainers. When the student gets in trouble he adds power and lets go of the sticks. The airplane levels itself and it begins to climb. The Kadet was designed that way.
It was designed to climb when power was added with a .40 engine, not go over on its back in a large egg shapped loop!
It flies perfet with a .40. With the .46 I was wasting the engine flying it around at 1/2 throttle. A .65 would be a larger waste. A plane ole K&B .40 works just fine, though thinking about a slightly hotter .40 for hot days.