Loading Rolls 

We use 5 1/2 O.D. pipe 5/16" wall and better for our loading rolls which are at each end of the mat.   
We use 3/8" plate for our end caps on the roll ends so as the loading sling doesn't slip off.
We weld these end caps with 7018 welding rod, the stick process to ensure good penetration and double pass for insurance the ear will not fall off.