doesnt matter if your ehxuast was welded to the chassis it would still knock. Its where the v shaped bit goes over the rear beam, get people in the back the beam is even closer to the exhaust. I had mine reshaped at a drive in ordinary exhaust specialist. they got it white hot with a blow tourch and bent it a bit.
Why not drive into somewhere like kwik fit when they are not busy and let them sort it out for yer. they'll probably do for less to nothing if they are not busy and da boss aint lookin. I used to do that with my old car. But this one seems fine for now.