All, with this post I know I'm really overthinking, but it's become a real educational experience in how the different variables work together.
I metered the location at about the same time the portrait will be done. At 400 ISO it comes to f(22) at 1/60. At 100 ISO it is f(11) at 1/60 or f(16) at 1/30. I believe that a heavy C33 on a tripod, with cable release and flash should be able to go at 1/30.
Using the angle of view of my 3 lenses, the 80, 105 and 135, I calculated that a subject width of 12 ft would require camera-to-subject distances of about 13, 16 and 20 feet respectively. According to specs, all 3 lenses will provide plenty of DoF even at f(11) at those distances.
I am not yet fully understanding the charts that came with my Minolta 360PX automatic flash, but it might have trouble giving full illumination for the ISO 100 at 20 feet.
This being the case what combinations of lens, ISO, f-stop and shutter would you recommend?