Hey hutch I have a hf flux core welder that I modified about a year or two ago, change the ground clamp on it to something hefty, same deal if you add a cap to it, it has to be the biggest one you can get, I also added a choke coil on mine, but the biggest improvement besides those to my machine was modifying the pinch roller that feeds the wire to the machine, it's pretty simple actually, it's just a clamp with a skateboard wheel bearing on it from the looks of it, I went down to the local bearing distributor and asked for one that had the same inner diameter but 2-3 mm bigger on the outer, just changing that makes the wire feed speed more constant and you shouldn't be getting as bad welds, also clean you material before welding, take a wire brush to it and leave the metal shinny that improves on your final welds also.