With the price of Sinar equipment being so low these days- I think a F2 is an excellent choice for portraits. The Bino Reflex housing is very cheap now, and coupled with a Sinar fresnel- very effective.
For portraits, I would consider getting the Sinar auto shutter. If set up properly it is extremely quick to use- the shutter automatically closes when a film holder is inserted, and opens again when a film holder is removed. It also allows you to control the shutter and aperture from behind the camera- another major plus.
Being that they are now a fraction of what they cost ten years ago- its now a viable option for the non professional or independently wealthy. DB mounted modern lenses are also probably one of the biggest lf bargains out there as well these days.
Using the auto shutter also allows you to use barrel mounted lenses easily- a major plus.