how good is chemical metal?

[vanordinaire]

My ford ranger back axle/diff was rusty and weeping a bit of oil. I cleaned off all the rust and found the casing was quite thin and there was one pinhole about a third of the way down the diff, well above the fill level. It's a '54 plate so probably not worth buying a new axle for so I'm considering looking for second hand one or welding a plate over the thin bit but both will involve a fair bit of work. After I cleaned it up I had to move it a few miles so screwed a self-tapper into the pinhole and slapped a 4mm layer of chemical metal over the weak bit, topped up the oil and drove it home. That was about a month ago and I haven't had a chance to do anything more permanent but I've been running about on our land since (probably done about 50 miles) in both 2 and 4 wheel drive and had a look tonight and it looks fine.
Wondering now if I could run it like this on the road.
Anyone had any experience of Plastic Padding's Chemical Metal and how tough is it?

[vanordinaire]

The diff in my OP is holding out fine after six weeks and just passed it's MOT on Thursday. I pointed the repair out to the tester before he started and he gave it a few extra pokes and digs and declared it fine. He said he's seen a few repairs like this mostly to sumps and never had a problem.