For less prestigious exhibits than the State Building, I usually print 10x14 and mat and frame to 16x20. Precut window mats in quantity from Frame Destination are no more expensive than the mat board. Frames from FrameFit are close enough to Nielson for the local market. Having all photos the same size makes a neat exhibit. Transportation is easier, too. Buying in quantity saves money. Purists will say that bottom weighting the mats precludes using one mat for both vertical and horizontal formats. I cut bottom weighted mats for years, but now find that local customers don't demand it.