Here's an oddity... the V1 reported the 400 focal length correctly in the EXIF, but when I added the 1.7 TC it reported the FL as 950mm instead of the correct 680. That's off by a factor of 1.4 for some reason.
I tried using my Sigma 150-500mm OS lens with the FT-1. I get a message saying "attach lens". I guess the camera software can't recognize a non-Nikon lens. Too bad, the result would have been impressive.