Precisions on rails are an advanced technique. Even more so without any further room for error which comes by way of foam. Mess up and land a precision on your arches and you'll be hurting. Please be as careful as possible while progressing in this method.
I would highly discourage flipping in a concrete environment. Maybe that's just me. Too much room for error.
Can't go wrong with simple QM or balancing. Sometimes I'll just set up a short circuit of very simple vaults and tic-tacs.
@Jim
I disagree that there is any confusion in the scientific world on proper stride. I wrote an entire article on this way back when which is stickied in the gen fitness forums.
1b) I need to re-iterate, and I really don't want to sound like a bringer of doom, but this is a very important point. You would be surprised by the impact a tiny pebble, stick, or shard of glass can have. In high school, a friend of mine was walking down the sidewalk and tripped. Instinctively, he rolled, only to have his C7 land directly on a small pebble, and he became paralyzed.
How often you train barefoot needs to be very well calculated. My normal stomping grounds is a breeding ground for hobos, druggies, and punks. There is broken glass, broken objects, and just random crap everywhere. While training barefoot is a great tool, and I do it every so often, given this factor, I cannot train barefoot all the time.
Also, please remove the quotations from your name

4) Remember, if the anthropological studies are correct, we evolved to be able to run down a deer all day, over uneven ground until it died of exhaustion. This was waaaay before Nike, KSwiss, Montrail, etc. Our bodies know what to do...we just need to get rid of the coffins we've forced onto our feet since right after we were born and rediscover how our feet were meant to work!
EDIT - I'd argue and say that humans were never "designed" nor evolved to chase down anything. Sprinting is ridiculously taxing on the body and cannot be sustained for very long at all. Running long distances to catch prey doesn't seem very practical either. If anything, we evolved to manipulate a stone and a stick, combine them, and propel them through the air to pierce our prey. Why sprint like a madman when you have this wonderful, freely movable shoulder that can javelin a spear through the air?