I have and use a 7" f/3.4 Darlot Portrait (Petzval) barrel lens with a full set of waterhouse stops on my 4x5. Having the optic mounted in a shutter would make life so much easier. A Copal #3 I'm guessing would make the max aperture around f/4. An Ilex #5 would be the ideal shutter to use enabling me to use its maximum aperture. In looking around, I have yet to come across a Petzval optic mounted in a Copal, Ilex, or similar shutter. Is there a reason for that?