[Lynn Eades]

Jon, if you take a few links of track and put you hooks on the ends, the load on the rope draws them in.
The hoo end are about 5/8" (16mm)square, but are only 3/8" thick at the ends.
The opening inside the hook is 1 1/4" wide (31mm) The ring is a 5/8' (16mm round, with a 3 1/16" (77mm) id. The hole in the hooks has about 1/8" clearance all round.
The hooks have a 27 degree turn in.
You should be able to work out a functional set from that.
Do you know a keen blacksmith?

Robin's photo holds a good lesson. Use leather gloves. The won't prevent injuries but they certainly can help minimise the damage if you do something silly.