I think my small paintings on heavyweight paper look best matted and under glass, and I love the way the edges of this painting are not covered by the cut mat. The substantial size of the mat looks great too.
As for my paintings on board, I always recommend this floating panel frame made by the Metropolitan Picture Framing Company. You can order the frame online, and simply specify the size of the painting and the "float size"- the size of the gap between the painting and the frame. I always use a float size of 1/8 inch.
Just wanted to share.