Clayton... So the G-Claron you had failed to hold respectable resolution on 15x36 inch prints from 5x12 negs? That's not what I'm looking for. What about the 210mm Apo Symmar? It's advertised coverage is 305mm which is only 20mm shy of the diagonal of 5x12 film. I'm hoping I can get an inch of rise with little or no noticible lower corner degradation on 5x12. Is that a pipe dream? If so then 4x10 is looking increasingly more appealing.