I use medium tension on my SPDs (fixed wheel) compared to a higher tension on my SPD-SLs (road bikes proper). I don't unclip unintentionally but I like to feel a more solid click when I engage. Just a personal preference.

Oh, and I also have a bit of play on the SPDs. It's unavoidable, I think. I'm not sure how effective the zero-float cleats would be really, given the small overall design and the lever effect of your foot on that small area. I am willing to be proven wrong though!