Need to build and stretch an already painted canvas 4x6ft.

Hi, I would make the 2" x 1" rectangular frame for the 6' x 4' painting with two internal supports. The frame would be painted in black gloss paint. The canvas would be stretched 1 " over the sides so the finished painting would be 66" x 42". The frame would have timber triangular supports on the corners of the joints and the painting would be fixed with staplers on stretching. The shipping and packing charges would be additional.