Thanks Chris.
Evening,
The steel tow cables and the D shackles turned up, I ordered 18mm diameter tow cables which are each rated at 4.1 tons. There seems to be a number of ways in which the cables were carried on the front of the tanks in period pictures, in fact there doesn't appear to be a standard to how many cables are carried at all. Some pictures show just a single cable, some have two cables, some appear to be about 18mm in diameter, whereas some look a lot smaller and there are even some pictures showing what appears to be some carrying tow ropes.
I decided, in the end, not to add extra bands around the circumference of the hub but instead to machine a series of small grooves into the surface to help the polyurethane adhere.
That's all folks,
Jon