How do I set up a blueberry in a raised bed?

I have been raising my blueberries in pots, I'm not really sure what species they are but they are going wild in their pots, I'm now looking at putting them in raised beds in the garden. 1. How big should the bed be? 2. Can I get away with a raised bed that is only 1m across or should it be 1.5m? 3. Should I fill it with the azalea potting mix that has done it so well in the pot or is there another option? 4. Could I do half azalea potting mix half pine bark mulch? Thanks for your help!