Hi Bryce...If your talking M20 the 'pannier support tubes' fit behind the bag carrier frames...
They are tubular with one end flattened and drilled through. This end fits onto the frame stud located at at the lower ends of the rear mudguard stays...
The tubes also have brackets welded onto them..
One bracket extends towards the rear wheel and picks up on a stud that is welded to the top of lower rear mudguard stay...
Two other brackets extend under the rear of the bag carrier frame and are bolted to the bottom of the frame with nuts and bolts...
There are good replica of these available and as both sides are not the same dimensionally, buying them would be the easiest solution...
No doubt someone will post a picture...I don't have one...You will then see a picture does tell a thousand words...
...Ian
email (option): ian@wright52.plus.com