Hello,
I was looking if you would be the author of the article about the Sturmflieger in the next issue of Aero Journal, look like I have my answer
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For your questions, I have no definitive answer but here's some hints :
The Fieseler's aircraft factories in Kassel that was producing the Fw 190 A-8/R2 was bombed numerous time during Spring and Summer 1944 and greatly reduced the production. Also the Rüstzustand 2, as implied by its name, is a factory modification and the replacement of 20 mm cannons by 30 mm ones was not a quick action (it would be also good to check the production figures of the MK 108).
Also we know some Gruppen of JG 301 were trained to Sturmgruppe tactics but used "classic" Fw 190s.