Well yeah, I would think twice about using it in places like Afghanistan or the US but I have never had any problems around NZ. I have an even more gun-resembling rig that is on a wooden stock and that hasnt given me any problems either.
The FS stock is a bit short but if you really wanted to it would be easy enough to extend it a bit or wrap some padding around the butt end. Presumably either Russians are much smaller than us (unlikely) or they tend to be wearing padded jackets!
I have tried three of the photo sniper type rigs. The first one I bent up from aluminium strip and had a front handle that controlled the focus, the second one is on the wooden stock from a .22 rifle and the third is the genuine FotoSnaiper. They all have the same issue and that is focusing as all the long lenses I have are manual focus and the Pentax auto focus adapter is, I find, just a little less than useless.
Here is the one on a wooden stock
Photo not taken on a Pentax!