turning bowls + lathe recommendation
If you really want that lathe purchase to be you last I would vote for the Powermatic. To turn large bowls: First rough turn them wet, leave the walls about 1" thick come back in about 6 mo to a year and finish after storing the rough blank in a dry place. I store them in my outside work shop and bring them in the house about a month before turning. To get the bottom perfectly flat isn't necessary if you use a face plate and screw the blank on securely. I have a large outboard faceplate that has about 16 holes in it for screws and the holes are angled toward the center of the blank, unfortunately, I don't know where it came from, but a big faceplate with lot of holes and big screws should work - leave enough scrap at the bottom of the bowl to cut if off the blank with a parting tool when done. I'm not sure I completely understood your question, but hope this helps.
Trying to dry the entire blank before turning is probably going to get you a cracked blank.