I started by making two rectanglular frames, that would each cup their respective pannier on the outside edge (front and back), on the under-side, and inside at the top... This is difficult to explain, drawings needed I think, anyhoo, I`ll struggle on and put up sketches later.
I`m pretty sure I used 20x20x2.5 SHS (Square Hollow Section) mild steel, and 30x6 flat mild steel, and a bit of weld mesh.
These allowed about 3mm clearance around each surface, for me to add rubber later on in the process (to avoid metal to metal contact).
I then cut, drilled and welded tabs to these frames to mount the Protex fasteners.
Then, using strips of inner tube, I attached the panniers to the frames, and offered each of them up to the bike.
Positioning them as best I could, I then fabricated mount struts to attach to the pillion footpeg holes, seat strap mounts and rear indicator mounts.
To stop loose luggage from touching the exhaust, and to give extra tie-down points, I added two triangles of weld mesh.
Lastly I added a 'Bumper Bar' tieing one side to the other, and hopefully adding a bit of protection should I get hit from behind.
I welded little pads over places where water could collect, had the frame powder-coated satin black, and bought plastic bungs for the exposed open ends of box section.
Sitting here in Istanbul, 42 days into my trip, I still have the burn marks on my arms from rushing through most of this process in one day, with a good buddy of mine, and a savage hang-over.
I am very happy with the outcome overall. Not to say there aren`t things I will do differently next time.
Again, time will tell how strong the system is.