Where to begin here....For starters could you please be a wee bit more specific about where the hole is ? Chassis rot from inside unless regular treatment with rust prevention products. Slapping a patch over the hole won't work. You have to cut away all the rotten chassis and fabricate a flush fitting patch which should be mig welded into the space. Depending on the location and extent of the holes you might be better opting for a replacement section of chassis rather than a patch. Unless you are confident and experienced at welding get it done by someone who is familiar with landys and welding chassis. Just patch welding a rotten chassis is the same principle as trying to patch a hole in the hull of a rotting boat. It'll fail somewhere else. You can get full, half, quarter and rear chassis sections as well as dumb irons and outriggers. There are various reputable sources. You don't need to explain it here just reflect on what is the right approach; patching may not be the best option.
