i've just watched some of PBusardos review for the russian and the russian 2.0 and he measured the center pin hole size and it's around 3.0 mm as opposed to the around 1.5mm of the kfl/russian91%.
so i'm not sure anymore it would be suitable for a restricted MTL.
Here's a pictue of a V1 nano, V1 full size, V2 full size, and a Version 2. The Version 2's chamber, chimney, tank and top cap are the same as it's smaller brothers. So you could convert the Version 2 to use a nano tank to make it 'smaller'.

As to the PB measurement. The center pin opening is only slightly bigger than the standard one's, which is the same size as a KFL-Lite. It's not 3mm in diameter. Are you sure he didn't say the air hole on the base of the Version 2 (look at picture above) is 3mm. I measured the air hole and it is 3mm. Behind the ring is a tapered channel, when the ring is rotated along it, it changes the airflow. You can adjust it to draw like the standard R91. I measured the ID of the 510 post/airway on the standard at 1.5mm and the version 2 at 2mm.
