I picked up my 115volt spot welder on tuesday and started to modify it tonight. I took the lower tong and cut it at the elbow. I then grinded it down flat and drilled it then tapped it to 5/16 - 18. The original tip threaded right on. I went down on the underside and grinded it down along the tube about 4-5 inches in length. It still needs fitted inside the receiver to make sure it will fit. I did try it on some scrap metal and worked like a charm. Tomorrow I will fit it on the inside of the receiver and post some picks. I thought I read an earlier post of heat treating the rails and x,y axis 1st then welding the rails in.