I will find my book on the D11 as more then 7 were built. I know off hand of 2 that were in active front line units, one being JV44 PLattzschutzstaffel, and the other belonged to a Major, can;t recall his name right now been awhile since I dug through my Luftwaffe books.
And the quote you have Krusty is what I am goin on here, they didn't use MW-50 at 37000 ft, GM-1 would be used in that instance. The D-12 was a monster below 20K, and would be the choice 190 ride if it ever made it in the MA. Doubt it, but I will keep looking. If memory serves me 452/3 was achieved below 20k.