After about six months of riding around with the rear shock canister (mounted in the same position but) zip tied to the frame rail with a rubber sleeve, I finally go onto making a saddle to clamp it properly.
Zip ties removed and waiting for the saddle install.
I quickly whipped this up a few days ago from some 40mm ply that I painted and cured in the oven.
I just so happened to have the correct (exactly) holesaws for both the frame cross member tube and the canister diameter.
Easiest to get at (tighten the stainless clamp) from under the tank.
The saddle shoulders onto the frame rail and the canister pulls up against it with a large hose clamp.
Quite a shade tree solution but it secures the canister very well in deed, and is up and out of site so no one would really know what it is made of.
I think it turned out really tidy.
Didn't cost a zack as I had the hose clamp laying in the junk box, and there is a shitload of 40mm ply that I salvaged from a casting mold manufacturer many years ago.
Very happy with the outcome...
Back to riding now.