I was trimming my pattern plane and I found I have to give left aileron trim to fly level upright. I then flew it inverted to check if it continued to fly straight and level. I found the plane tends to roll to the left. I thought this would suggest that the right wing side is heavy. When I checked it, I found that the left wing side is heavier! Any one out there has come across this experience and found the cause and solution? Appreciate your help on this.