There are many lenses in 39mm thread mount not made to the Leica standard. The Braun Paxette? Lens screws on, back-focus is different. Contax lenses mount on Nikon cameras, but do not focus correctly.
The FSU thread mount is built to the Contax standard, and the Leica to its own. The Nikon S-Mount is built to the Leica standard focal length. Same problem, different mount.
SO: the J-9 can be used either with the Russian camera, OR with the Leica standard. On the latter you have to hack it.
I've never used a J-11 in Leica mount, but the one for my Contax is PURRR-FECT.
J-11, 13.5cm F4 wide-open on my Contax II, CLA'd by Eddy Smolov.
Late (1975) new-old-stock J-9 wide-open at F2 on the same Contax II, same roll of film.
I had to shim the J-9, added 0.5mm to the shim. I did not have to adjust the rear shim.
So: Kiev mount Jupiters on the Contax: you might need to adjust the main shim, but probably not the focal length.