A 32" is a lens with 1.25 diopter or two +0.625 for better quality. A 40" lens is +1 diopter, or two +0.5. The field curvature would be wonderful, sharpness so-so unless stopped down, but you would not know until you tried. The Leitz 560mm telyt is an achromat, that means sharpness in center is doable with the right lens. You could start with a Canon 500D.
Not sure how a 500D fits into build or lens discussion of a 20x20 wet plate camera, but I'll sleep on it.