I tried this screw arrangement out on the school’s cross country course yesterday afternoon, but it was so stunningly flooded it was hard to tell if my shoes had better traction or not.
If nothing else, this short test run did alleviate any concerns I had about the screws poking the bottom of my feet. (This pair of Saucony Kinvara 3s is fairly lightweight to begin with, pretty worn out, and has yet to be fitted with its new insole, so there’s not a lot of padding there.)
The screws I used were No. 6, 3/8 inch. (Other posts I’ve seen have recommended No. 8, but my local hardware store didn’t have those.) I just made a tiny hole with the screw tip and then used a screwdriver to work the screws in. Takes a little patience, but not all that much time, really.