I'm 10 miles from ocean half way up a hill that gets good airflow. My microclimate (10a) is a bit warmer during the summer and cooler during the spring and winter. Pierce will self pollinate better than the others but I will have smaller but fully developed fruit if I don't pollinate them. Those are the fruit I thinned.
Brad, this is the 3rd year of non developed fruit. The fruit in the picture was pollinated middle of March when my tree was just flushing. There are a few more seedling fruit that are even smaller.
During the periods of intense heat, the cherimoya trees do shut down a bit, but Pierce fruit does continue to develop. Now that cooler temps are back, trees look good again. It's either a crappy seedling or, as, galatians522 mentioned, it may not like this microclimate. I'm more than happy to give scions away when I cut this thing down to graft more knight and Pierce to it. Maybe someone wants to experiment (doubtful). Many other varieties I acquired in last couple years have not fruited yet (I'll let them next year) and I'll see if they'll have problems. I doubt it. But with his easy pierce has been, definitely going to top work that to this tree.
Here's a picture from last year's fruit that didn't mature. It's about the size of an 8 ball.