I have owned my 1973 140 for two years. While my heater works well, air leaks from the plastic housing at the base of the flap handle and the trim wheel (between the seats). When the OAT is low (below 32) the cold air blowing into the cabin is awful. I have to place towels over the flap handle and trim wheel to block the flow of the cold air. This makes trimming during flight difficult. Has anyone had this issue and if so, how did you solve it? My plane is in for annual right now so I thought this would be a good time to look for the solution.