I've searched far and wide and found many different opinions. My dealer doesn't have any rail kits in stock and said he wasn't sure if he could get one soon. I've heard people say they made them with 2x4s. My issue is that the rollers on the insert are about 3/4 inch off the hearth so getting a 2x4 under there wouldn't work. My hearth is 2 1/2 inches high so I can't just pull the unit out either. Maybe build a box 2 1/2 inches high and some 3/4 inch metal strips for the rollers? Any ideas? What are you new 52i guys using?