Originally Posted by morski
As long as you cutting and welding at the original seams and welds where the factory ones are then you will not alter the cars structural integrity. The car body is originally put together in sections anyway and held to egther with mainly spot welds seam welds and of course some almighty glue.Of course this is dependent on your welder/bodyshop doing a good job.
There is no lateral seam in one of these bodies. At some point you are going to be cutting a structural piece in half and welding it back together. In the end, it's going to be structurally unsound. But what the heck, there are lots of mods being done to cars and they seem to hold together well enough.