I have a 2008 G35 with a noise like a loose part when going over a bump. I just took a good look at the underside and discovered that a cross brace that attaches to the transmission at it's center and catalytic converter flanges at either end was loose due to the flanges rusting away. The brace is in good condition but I don't think the cat converters are in good enough shape to weld to them.
Is it worth strapping a flange to them to reattach the brace or should I just leave the brace off?

 

I'd weld on a tab and reattach it, looks like plenty of meat right above where it broke off.