I talked about this once with Scott. A pipe can be repaired, including welding, if it is obvious that the pipe repair did not alter the pipe from its original design and specification. For example, a pipe can be welded if it cracks but if the weld goes a full 360 around, its not clear if it was a repair or an alteration that changed the length of the pipe.
I think such a repair as you describe should be acceptable but in doubt, its always best to check with Scott. He has the final say on such matters.