Thanks for ironing out the details Dave, and it's nice to know that the stories are actually true for a change.
Now it's been a Very long time since I have considered the strength of Con Rods so please bear with me cos there are likely to be some errors (no change there then
).
If memory serves the loads excerted on the con rods are proportional to it's mass and the rpm, but the important bit is that the forces on the con rod go up by the fourth power in relation to the mass.
A heavy cast rod would have a much lower rev limit than a high strength fully machined from billet and lighter "after market" rod..
So it will come as no surprise that lightening and balancing of production rods help to raise revs.
Now i'm sketchy on this and I don't seem to be able to find anything in the reference material I have to hand but someone out there will know.