One thing to be careful of is where you locate your ground cable clamp - in relation to where the actual welding will be conducted. Avoid putting the ground clamp in a location where a ball/roller bearing (like the wheel bearings) would be in the path of the electrons as they flow from the stinger back to the ground lead. Ball/roller bearings are designed to have almost zero surface/surface with their races. They roll across the race on just a microscopic point of contact. The point is, as the current produced by the welding machine flows through the minimal surface area that exists in the bearing, they can get hot. If they get hot enough, the can become distorted.
Even worse, is if they are loose - I mean like loose enough that gaps exists between the races and rollers. The flow of electrons will arc as they cross the gaps and destroy the machined surfaces. Unlike the damage caused by heat building up, arcing will happen immediately - given the right conditions.
But if you are just welding on the frame - like doubler plates or filling cracks - neither of those things mentioned above should be an issue.
But do try and clamp the ground cable close to where the arc will be struck. Taking it to the extreme, if you grounded the machine back at the rear end (say to a frame rail crossmember or bumper bracket) and then dragged your stinger to the front end to do the hot work.
Your passes will get better penetration because of the reduced resistance - without cranking the heat up. Using that reduced amperage will give you more control over the weld. The beads will be more uniform and the final result will look and perform like a professional job.
