Originally posted by rdbates:
.. would that cause a risk of breaking the welds and causing a failure of the frame?
How good a welder are you? If your welding is up to the task its just precision work. If your welding is not up to the task you are risking a dangerous failure.
There are other options. You might think about widening the fenders instead of narrowing the suspension. The welding has to be prettier, but a failure is not nearly as scary.