That thing has been phased out of service for along time now. But everything I've seen has gunner sitting on ground with tube over shoulder. That thing had a real bad back blast, dont know, probably. But only 1000 meter range. It always kicked up tons of dust when fired.

So ya, I bet you could fire it off shoulder standing......but to guide missle it flight? Probably not, or at least not well.

Best would be to have gunner sitting when fired for realism.