I placed 153 saber studs, (1.0175) in my F-7. I have only ridden it on ice and was a bit dissapointed. Not in the sled, but in my choice of studding. It would break lose when pushed. In fact, it made for a scary experience as I tromped on the sled while doing 40 mphs, and it broke lose between 40 and 60 mphs. A Little unsettling. I encourage you to go with a longer stud such as a 1.175 or more than the 153 i placed in. The sled had such impressive acceleration that I got the clue real quick that studing should have been taken more seriously.