Spoke too soon on my previous issue...
Running WP 2.91 and Pie Register 1.1.3, I am unable to add User Defined Custom Fields. Aside from this issue and the image upload error, all is well.
Design Bug: I need to disable Paypal in order to register a new admin, contributor, author or editor account. I would like to see a work around that uses Paypal only on the Subscriber level and not the other user levels so staff accounts can be registered without having to disable Paypal.
Hope the membership plugin is going well and will see the light of day.