RE: About O.S #8 plugs!
BW,
What the man sells does not negate the truth.
The OS plugs are too short! OS did not respect the industry standards for long and short reach glow plugs. Therefore they don't fit most other engine makes that do respect the standard for a long reach glow plug.
We engine designers have spent a lot of energy fitting the glow element to the combustion chamber. It does yield very favorable results to have a properly fitted glow plug (element).
As for durability all you need to do is time it. In a high performance set up (like a pipe) the time is measured in minutes (less than an hour) in most cases.
So in an OS head the glow plug might be more suitable as it might fit the (non long) chamber. Also the rather low compression ratio of most OS engines might contribute to a longer life for the anemic OS #8 glow plug. I assume that as a system the OS engine and glow plug might perform better than they might if looked at as separate components.
The truth found through hard analysis is still the truth no matter how hard one wishes it to be otherwise!
All the best,
Konrad