Fabricating a 4 ft trailer extension. How I'll square it up to weld it together: Cutting square holes today to bolt mount it with square tubing and battleship plate steel. Is there a formula or rule of thumb to determine the ratio of how far back the wheels need to be on a pull trailer to prevent harmonic wobble vibration of the whole trailer at highway speeds? If I add 4' to my trailer, it will be 14' from the hitch to the pivot point of the wheel carriage, and 8' from the pivot point of the wheel carriage back to the rear end of the trailer. I'm wondering, will I luck out and that be far enough back from the center of gravity of the trailer to prevent disasterous wibble wobble of the whole trailer, so that I don't have to create a new pivot point mount and move the whole carriage back a few more feet.... or.... Floor lenght of the extended trailer would be 19.5'... so roughly... 11.5' of floor ahead of the pivot point plus hitch in front of that, and 8' behind pivot point. Not a huge ratio difference, I know, but still behind the center of the trailer floor body by 1.75'. Is that pushing it? ~ I suppose, as a note to self, once the trailer is enclosed, I should remember to put my plane in tail first, so the main weight of the plane (engine and all) is at the rear of the trailer instead of the front.... to further add more weight behind the wheels to the rear of the trailer and alleviate the situation, rather than worsen it. Or wait, maybe it should be the other way around, with more weight between the trailer wheels and truck wheels, to add braking power. I'm guessing this is about as much about trailer loading management as it is about wheel location, and in the video the guy has his weight inside the trailer all forward or all back. ~ I was able to fix my wire welder feeding/spurting problem by removing 2' of the feed line tube that goes to the gun and adding some corrugated plastic reinforcement tube around it. As the welder was designed, it was just too long of a feed tube and causing too much friction, esp. with the kinks the line got over time. Works like a charm now, at least, for what it is, a bargain basement welder. New modified welder.