I had my oculus touch set up and I was playing the bullet train demo the other day and I noticed that every time I moved ever so slightly when I was in the train car, the Guardian system guidelines appeared. This despite the fact that when I set up the guardian system, it said my play area was "moderate." I couldn't even shift my weight from one foot to the other without the guardian guidelines appearing! It was very immersion breaking! This is how I resolved the problem:
I have a chair mat on my floor in front of my computer desk to protect the carpeting. If I take off my shoes (or house slippers) and stand right at the edge of the chair mat, I can feel it with my left foot. This has the added advantage of taking me away from being right in front of the computer screen.
I turned off the Guardian system completely. I don't need it, because I know exactly where I am because I can feel the edge of the chair mat with my left foot.
This ties in with a clever idea I read on C/Net or somewhere. If you are playing on a hard floor, you can get a throw rug that is roughly the size of your play area. That way, if you play in your stocking feet, you can always feel when you are in the safe zone. If your playing area is already carpeted, you can buy a couple of chairmats from the office supply store to define your safe zone.
Physical safeguards like this will probably be better than the guardian system for most people. Hope this idea helps someone.