Mine took years to get established, but are in full sun all day without issues this year. I'm somewhat inland, hotter than on the bay. They're about 5 ft tall, from bare root planted in-ground in 2018 I believe. I planted 6 but 2 died. Not growing fast yet, probably have doubled in height in 4 growing seasons. If I had to do it over again I'd direct-sow seeds. I bet I'd have bigger trees by now. I used shade cloth for a year or more, don't remember how long. I actually had my drip irrigation get shut off for a month this summer before I noticed. I'd been giving the pawpaws a little supplemental water, but not much. They didn't even look bad.
I think 3 of the 4 have flowered, the biggest ones. One has set fruit two years in a row, but dropped them after a few weeks. They set fine without hand pollination.
I don't understand the flowering cycle for them. Mine are covered in flower buds now, which probably won't push/open until spring, but they're still fully leafed-out, and haven't seen chill hours in months AFAIK. I think I had one open a flower in August once.
They look like they might push new leaves now, leaf buds are swollen, but I think they'll wait for spring. I only get a few pushes/flushes a year, in the spring. Mexican katydids eat holes in the young leaves as they emerge, but aside from that they're doing well.