8 posts were split to a new topic: Building a better worktable?
have you tried using the side rollers with Square wire? I have the C150 “D” grooves sizes 4mm, 3mm, 2mm, 1.5mm Durston tech emailed me and advised that you can start with a square and in regards to the size, it will be trial and error and may be different for each user not much help 
I tried with square didn’t come out too great. I edges needed to be filed off. Worked better starting from round