I have an Arca-Swiss with extension rail, standard bellows is I think 40cm and I can pick up a longer one at around 60cm.

Also have a APO Sironar-S in 210mm (plasmat), but is simply too contrasty/sharp for portraiture.

So if Ektar is a tessar design, what lens design is Commercial Ektar? I know APO Artars are dialite designs, same as APO Ronars. The APO Ronar I saw recently (in barrel) was huge and heavy, quite different from the one shown here.

Both candidates have round irises in the shutter. One is about 1 stop faster than the other.

Both of the lenses I'm currently looking at are in #4 shutters, Ilex and Acme.

It sounds like the Ektar is the preferred one, I've never heard about "harsh Karsh" before, his portraits are legendary.