So I have made a test flight (version 1.0.1) to check the drag, my plane configuration was 170lb on pilot seat (rest of the payload empty) and all tanks at about 70% (reserve tank at 100%). I took the throttle fully back so it was in idle, when I reached 150km/h I watched for the plane to get slower. At a vertical speed of 0m/s (continually pulling the yoke back) it took me a whole minute to get the airspeed from 150km/h to 120km/h. Considering the idle spinning propeller adds a certain amount of drag on its own, even without flaps or gear, it should decelerate much faster, I don't know where the energy comes from.
Even on final approach with landing configuration (gear down, flaps 30°), throttle at idle when I dipped the plane a bit down down, I was instantly at 150km/h again and when pulling the nose back up, it took a great amount of time to lose that speed again even with gear and flaps down. Adding flaps and gear has only a negligible effect on drag.