My first fall due to clipless was after I had unclipped and put my left foot down, on the ball of the foot, like ya do. Said foot slid forward and out from under me and I most ungraciously hit the pavement. I quickly learned you don't do that. My shoes have a rubber bit on the heel that I now make sure to put down first.
What I really want to do is put on a rubber thingey like roller skates used to have on the toes. Not only would you not slide, but imagine the push-off you could get!!
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Phazer
waiting for inspiration