Interesting thread. I have a Shen Hao wooden 4x5 folder, with a nominal bellows draw of 360mm, but that includes a bit of fiddling with the rear standard, which is fine, but it is fiddly. Real world bellows draw is approximately 325mm.
I have a Tele Arton 250mm lens, which I specifically bought for portraiture and for pulling in whatever needs pulling in, in front of the camera.
I also have a Komura 400 T which for all intents and purposes is identical to a Fujinon 400 T I shot alongside of a couple of years ago. In fact we swapped lenses and took a sheet or two with each others lens. The results were interesting, there didnt seem to be much of a difference, in fact when we met up to compare negatives and prints, there was pretty much nothing in it.
Upon reading this thread I decided to end a beautiful summer day with a bit of fiddling. I pulled the Shen Hao out, then placed the Tele Arton 250 on and then used the same distance from the film plane I generally use for a single portrait, 156cm from the film plane to the front of the subject. At this distance I know I get a full bust shot in portrait mode. That is, if the subject is standing with their arms folded, I just get the bottom of their folded arms with a bit of space above their head.
Moving back about another 10cm I have more fiddle room for when enlarging, meaning I can decide which vertical side I will leave a bit more space on. I have found that I prefer one side with more blank space, as do many of my subjects. Sometimes though, the person whose portrait I have taken, prefers or needs the other side to have more space, so leaving a bit on both sides, works well with this 250mm objective.
Not having a suitable subject, I used a potted tree outside the garage, picture 001. The rest of the Tele Arton pictures are self-explanatory. I did entertain the thought of a 270mm Tele lens, but firstly I didnt find a suitable candidate at a reasonable price. When the 250 came up I grabbed it and have been fairly happy with it in using it for portraiture.
I next placed the Komura 400 T on the camera, then racked it out carefully as it is a heavy package on this reasonably light camera. I needed to pull the camera back to 285cm from the film plane, this extra distance can be seen in picture number 001. I left the camera in standard mode to show what could be reasonably attained without going to the extremes of bellows draw. At this extension I know I can get a great bust portrait, and have.
I have used this Komura 400 T on my Toyo 45G monorail, when running a bellows draw of around 450mm, this lens produces some really dreamy stuff and one is certainly looking at primarily producing a head shot with this extension.
I would suggest a minimum of 250mm as a starting point, 270mm would be better, a 300 T would probably be the best all round if you go the telephoto route. The 400 T of pretty much any manufacture is quite heavy on a light camera, not to mention on your tripod. However a 400 T, it is doable.
Mick.