Mat, a petzval that covers 8x10 at infinity will usually be quite large. You can get away with say a 9" lens for portraits closer in, but ideally you need around a 12" lens to cover 8x10. So your 13" choice would be quite good. Unfortunately, the lens board size is the limiting factor. A deardorff lensboard is roughly 6x6", meaning you need to be careful in finding a lens that would fit... Especially if it its a fast petzval. Some of them are wider than others, but they are available if you look. I know that most petzvals that. Work for 8x10 are fetching huge number now on E'bay etc and the used market in general.