Something like those hard plastic shoe/boot mats is a good example of something to set your pots on. They usually have a raised pattern on the bottom that would prevent the bucket kind of sealing to the mat and prevent drainage.
The bigger the container the better, but i'd recommend a taller bucket rather than a wide low profile.
I don't suppose you would have a link to his thread would you? Pretty please??
5 is fine but if you have the room trust me 7 is better. It's all a matter of setup as well. I yield more in 7 I used to have pics of 5 under same setup I use now. But now I use only 7 unless I'm out or there being used. Try it side by side for yourself and decide.