Walter, your recommendation is perfect, I have often surmised that lens would be a nice addition, however their scarcity in this country at a reasonable price, makes for a glum outlook.
Instead I have been on the lookout for a Fujinon equivalent; Fujinon C, f/8.5, 300mm in Copal 1 shutter. It also sports the 52mm filter size, so that is workable as I run two filter sizes, 52mm and 67mm. Interestingly the Fujinon is lighter than the Nikon unit, which did surprise me, 290g versus 250g.
On paper the Nikon should be the better performer, but the reality is that for what I and most other photographers do with these lenses, either would probably be better than what we can imagine they may be.
My Shen Hao wooden folder has 360mm of bellows possible, however in reality and unless you really do fiddle a bit, about 320mm is more like it. The 300mm lens is in the background as a possibility if one turns up at a price I find doable, but I'm not in a hurry as the 250mm seems to do all I wish for.