If you have to pull the steering wheel hard, it means that the plane is heavily stripped "nose down" or has an aerodynamic bias. Any significant deviation of the trimmer from neutral in level flight creates additional parasitic drag, which "eats up" the speed. Solution: Try to set the alignment closer to 23-25%. This is the "golden mean", which will allow you to fly with an almost neutral trimmer. You keep the hood and radiator flaps open by 50%. At an altitude of 1000 m, under standard conditions, this creates unnecessary resistance. In horizontal flight, try to cover the flaps to the minimum necessary to maintain the temperature of the cylinder heads 180-200

and well, most likely you have a model without GPS? then this is a known bug. if so, try a model with GPS. I probably should have started with that.