When I was refitting the exhaust pipes on the Fastback the other day I thought about a common complaint (which is more of a misconception, really): "they come loose!"
There are two things to distinguish here: one is when the finned lockring (062464) actually comes loose and unwinds from the head.
The other is when, despite the lockring being nice and tight, the exhaust pipe moves and rattles.
Before anything else, be sure to tighten the lockrings and give them an extra nip when the engine's hot. Do this with a proper C wrench that fits well, possibly the proper lockring spanner (063968), not with a hammer and a screwdriver, that's just cruelty to engineering.
To address the first problem there is only one thing to do, you must use tab washers (062412): these make it impossible for the lockring to come loose, it's as simple as that. There is no reason to do anything else, such as drilling holes in the cooling fins to then hook springs or lockwire. Some savages may think it looks "cool" and "racing" but it doesn't. Again, it's just cruelty to engineering.
However, even with the lockrings secured, the second problem can still manifest itself, but this is not due to the lockring loosening: the culprit is the sealing washer (063995) that sits between the exhaust pipe and the head. They wear down, creating just enough of a gap for the pipe to rattle.
The solution here is not to tighten the lockring further, which can damage the threads, but to replace the seal washer with a new one. Carry a couple of sealing washers in your road kit and show everyone how knowledgeable you are when the rattle disappears after a quick roadside repair!
Here are the parts in question; the C wrench shown was made by the legendary Giacomino "Jack" Latini a very long time ago, and given to my dad when he closed shop (I'll return it as soon as I'm done!):