Well, I used a plumbing cap for the foot, but I did pound a little bit of dome into it. Also, once you walk on the asphalt some, the surface gets roughed up and grabs the ground like a bopper grabs the knapping surface. It won't be slick for long.
My mom's foot has been hurting for a while, so hopefully this will help with her mobility. It's hard to see the parents getting old.