Update: Simon and Mick helped me get the AVO mid lifted on its hangers.
I wound up using the stock rubber cookie, and 2x thin rubber cookies all on minimum possible distances to raise the mid by maybe an inch or two.
We put the Lib on stands on its side and jacked the passenger side rear wheel a little to provide more clearance in order to raise the mid pipe, also jacked. Obviously anyone sane would seek assistance from an exhaust professional, but I like DIY
The result on a short test drive was much less boom from the zorst at around 1000-1200 rpm, little or no knocking in normal driving. Sounds much tighter acoustically, more impressions soon!
Hopefully, I won't be scraping on speed bumps either, which, including some observations from Bruce, were indications that the exhaust system needed some attention.