I'm getting ready for a show in a gallery and am wondering about a frame size for 15 x 15 inch prints. I have always printed 10 x 10 in rectangular 16 x 20 frames. I typically optically center the picture. Now I want to move up one size in paper. I use the Optical Print Centering website to help me previsualize this. To me, it looks like I need to have top and sides equal at the larger print dimensions. Also, the top and side borders look a little small (2.5 inches). The bottom is 6.5 inches. Any suggestions would be welcome. Is the propsed framing adequate, or do I really need to consider moving up one more step in frame size?