Somewhat improved welding. I took a lot more time on this the 2nd time around, making sure everything was clean and not getting over-ambitious with the welds. I still ended up with a few pinholes, so the weld was covered with a layer of "extreme" JB Weld which I have used before with a lot of success on exhaust manifolds. Got a bit of advice from a mate who looked at the hole in the exhaust and suggested I make a "birds mouth" that straddled to the better bits of steel. Welding involved a lot of short bursts to tack it into place and then slowly filling in the bits between. Its far stronger than the original mess and I'm confident it will be permanent this time. The unpainted picture is a lot of unsuccessful welding while I tried to get the wire speed and amperage right. The bit of steel was cut from a fat Falcon exhaust pipe which took a lot of amps to light up properly. I was messing up a lot trying not to blow through the steel of the catalytic converter as they are $500+ to buy and I didn't want to ruin it. On the floor in the 2nd photo you can see my original patch piece which basically fell off as the weld penetration was minimal.