I finally decided to try bending one of the flats with just a hammer and a couple short lengths of steel pipe. It took some time and effort but it didn't turn out too bad.
It needs some final adjustments including the obvious "bow". The left side holes got misaligned when I absentmindedly reversed my template but considering everything else it came out OK ...sort of.
"Dimples" on both sides between holes #7-8 (counted from rear) need to be applied and a final version may be ceracoated or parkerized to match the adapter.
My sincere gratitude to rccathy for his generosity in providing these to experiment with.