Tony,
I see what you mean.
Just the act of the fibres bending around the curve in the thimble.
I wonder if the weakness is cause by them cutting into each other or individual fibres within a strand under load or just the fact they are bent.
I don't suppose it matters, unless the knowledge can change the result.
The other method of termination you mentioned to me seemed a bit suspect at the time but given the way your testing is going it's starting to look like an option worth testing.

Interesting stuff.

Regards,
Phill

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!