What time frame did the Germans switch over from the box on the back smoke grenade launchers to the racks mounted on the turret/ top of casement? I know my Tunsian Tiger has the turret set up, so ...mid 42? Have a StuH 42 E/F (which I question. Thought the early StuHs were Stug F/F-8s) Also, I have a set of shurzen kicking around. What would the possibility / time frame of them as a retrofit?