Okay, I just finished a breadboard trial for the reset lines.

The circuit I used was a pair of 5KOhm resistors for the voltage divider, with one end of the divider tied to GND and the other tied to Arduino Pin-51. The diode connects from between the two resistors directly to the RST pin. Nothing else required, works repeatedly well for me here.

I am still using my original Pin-51 code.. haven't updated the Arduino since I got that working back before Christmas. But the power-on reset logic works even if I disconnect it from Pin-51, as it should/must do.