No need to cut the frame there. Cut the pipe off the flange, then turn it about 180 degrees. It will kick the outlet more towards the center and let you run it down with out any interference. Of course, as with everything else, test fit everything before you weld it back together.
EDIT - Looked back through some notes. I flipped the piece of pipe I cut off, not turn it. Either way, cut it off, bolt up the flange, then crawl underneath and twist and turn it until it clears. Then mark it, and weld.
Looking good!