Power level is a very minor factor, it's to get you to let Buffy-the-phone-girl be your engineering go-to, and buy a more $$ rod.
The relationship between rod tension (what breaks them) and reciprocating weight is linear (500 grams is 25% more than 400).
But it varies as the square of the RPM (and worse if the rod ratio goes down). 6,000 vs. 8,000 isn't 33% more (8 ÷ 6) but 78% more (8^2 ÷ 6^2)

IIRC Bill Jenkins said 300 passes 45 years ago (SBC), but he anticipated that there is a tendency to say "just one more time", so he advised hitting each rod with a big hammer and into the dumpster to stop anyone from doing that...

Aluminum rods are not inherently unsafe, they were used in 750 Hondas forever, and lasted 70,000 in Triumph 750 triples.