Good day, Ian
I confrmed the time frame for the /17 my source is Lexikon der Wehrmacht I Babelled the line on it's dates "This variant was however only manufactured starting from autumn 1944" there is a production chart as well.
Lexikon Der Wehrmacht then click on
Sonderkraftfahrzeuge
Now dates on the Walking Stuka were a liitle illusive, but I did confirm that production on rockets in general started a little before Barbarossa, and were in use, in a limited amount at the start of it. There is date references in the Both Links but nothing which pegs down anything exact
Luftwaffe Rockets
Lemire on Rocket Artillery
Hope this is of some help, I enjoyed the research anyway.
Eternal War(gaming) PanzerBob
