So a follow-up and thanks to all your helpful suggestions back in July.

PVG is NOT a good airport for int-int transfer as you warned.

I did change my HKG-PVG flight on CX to allow for a 5 1/2 hour transfer time in PVG. The CX flight was held for two hours in HKG by ATC so arrived in PVG 3 1/2 hours before DL flight to the US. It then took a good two hours to officially enter China, then walk that long, long "wenzhou trail" or whatever it's called from terminal 2 to terminal 1 and recheck-in with DL, then leave China again via immigration. Also, just as you predicted, the immigration officer on entering China had to call over a supervisor to let me in for the transfer even though as a US citizen I am allowed TWOV. Delta does not issue mobile boarding passes for China. Fortunatey I did not check in bags on CX as that would have taken another 45 minutes to claim baggage in PVG.

So I made it but wouldn't suggest it. Only did it because was able to get a low DL C award back to the US.