I did make one barn quilt with exterior plywood. Hung it on my garage for about 2 months and it delaminated....the layers of wood started to come apart. I questioned another presenter at our guild meeting and she said that they use MDO board (Not MDF board). This is not a typo...MDO board is correct. It is not readily available here but Home Depot will order it for you. Our higher end lumber yard ordered it for me. Now to get busy with paint and be sure to seal the edges and put some sort of frame on it...plastic to cover the edges or wood of some sort.