8 of the 12 built were sunk
Wrong. 7 were sunk by war activities, another 2 grounded themselves. And, at least, the quota is like for all Kriegsmarine ships... So please do not make the design responsible for getting sunk by outnumbering forces. One was hit by mines all others were sunk '44 or '45. So they were successful in '40-'43.
Hold on with your design. I'm interested to see it.