Andy - that is a great photograph!!! You should be thrilled with this one, the magic hour light is perfect! And this lens is so sharp and lovely DOF (or lack thereof).
Thanks everyone... Thomas, the Dallmeyer 3b is an 11.5" lens. It covers 8x10 as it has massive coverage for it's focal length. However it is a bit wide angle for 8x10. You are correct in that the subject looks different because of the 'roundness' or curvature that the petzval lens exhibits. Years ago, the photographers used lenses of way more coverage than was needed with smaller plates so as to keep more of the subject in the sharper center sweet spot, but also to isolate the subject from the background. For now, I think 6x8 or whole plate is the best look with this lens.