Here are some samples from the Nikon V1 + FT-1 adapter + TC 2.0x + Nikkor 400mm f/2.8 lens. The focal length calculation should be: 400 x 2 x 2.7 = 2160mm:
Nikon issued firmware update for the Nikon 1 J1 and V1 mirrorless cameras which adds pixel mapping and support for the FT1 mount adapter. The FT1 adapter enables the use of Nikon F-mount lenses on a Nikon 1 body. Here are the basics specifications: