Still on an autopsy, though I have to say I think those kind of graphite rods with the extended section below the lower grips are well flawed.
For heavy work when the rod is fully loaded, it relys on the butt section strength to give the rod its full power.
With those extended rods, they have moved the grips quite high on the rod, with a great length of unused rod extending below the lower grips.
So when loaded up the rod bends from the point of resistance which is most probably your upper hand and some on the lower grip, but mostly the section just above the upper grip will take the full brunt of the force at that small point.
Hence the rod never loads up to its full potential.
Correct me if I am wrong in my observations.
Dan