I recently purchased the spool gun without checking compatibility with MIG machines. Oops- mistakenly assumed it would work on my relatively new SP-175 Plus with the switch harness included with the spool gun. After some examination it is clear that the spool gun hose will plug into my machine and a 4-pin Amp connector can be retro-fitted for the spool gun's plug. The newer machines recommended for the spool gun obviously have a new circuit board design and socket connector layout different from my SP-175. The spool gun switch harness will absolutely not work on my machine without modification. At first I thought a simple SPDT toggle could be used to redirect DC current from the internal wire-feed motor to the spool gun motor, however, the switch harness uses a DPDT toggle to open the internal wire feed motor circuit and close the spool gun motor circuit from a different power pin on the CB. I wonder if this is due to different motor speeds required for the spool gun. Has anyone out there successfully performed the hack to make this combination work? Not wanting to go buy another new MIG.