Why not just get a longer lens?
The 150m would be a better choice... not to mention less expensive ($ 1,500 LESS), half as many contacts to go wrong and better optical quality... less flare
and sharper as well as better bokeh...
Unusual choice and recommendation.... shooting medium format for a slight quality gain and then recommending to shoot with a teleconverter on a short focal length lens?
The 1.7 TC adds 6 more elements. Is not specifically designed or optimized for the 100mm 2.2 weighs an extra 465 grams and costs $ 1500.
Not to mention the f-stop factor that has to be calculated on every light meter reading.
Heh, I'll tell you why.
1. With a 2.2 and a 1.7x TC I get F3.5 wide open. Versus the 3.2 of the 150mm. A negligible difference.
2. The optics of the Hassy TC are superb, this isn't a Canon Extender of which I used the MkIII's and sold them. Unless I invest in the 150mm 'N' which is hard to find used I can't perceive any performance difference or savings.
3. 150mm is a little short for me, even on the 1DX the 85mm feels a little short as I mainly use it for headshots. I like something a bit longer.
4. I now have not just a 80 and 100mm HC lens. I also have a 136mm and a 170mm so if I travel and do landscapes I have everything covered and relatively lightweight.
Or I could have the 150mm which is a tiny bit faster and that's about it. For me this is smart money.
With regards the other points, I have not noticed any issues with flare, I shoot wide open and can't see / notice any difference in Bokeh,
The 100mm lens is considered 'the' lens for Hasselblad, a used TC 1.7x can be had on ebay for roughly $600-$700.
The following image shot on the H3DII-39, handheld, at 1/125sec, with the 80mm and 1.7x TC (135mm) is rubbish isn't it? Look at that terrible bokeh and flare.