All right.
So on saturday I put the car on body stands and investigated.
I discovered that it was actually the muffler contacting with the tailshaft and not the hanger, which I was annoyed with as now I didn't have a plan on what to do.
Decided to see what I could do about "re-aligning" the pipes after the final muffler.
Anyway, took a bit of persuasion but I managed to move it across, maybe even a little too far.
Took it for a drive around the block and I didn't hear any noises suggesting the tailshaft was in contact with the muffler, though I wasn't overly happy with the clearance as it was only about 3mm off.
I might fine tune the alignment this weekend.