I guess one issue would be how much of the paper are you going to cover with mat material. If you are just covering the edges, I think I agree that 20x24 will be too small. If, however, you are going to have an inch or so overlap on each side, I can see how 20x24 would work. When I print, I tend to leave at least an inch of white on each edge of my 16X20s. so a 20X24 works well.