I didn't change anything on my rod when I converted my Saito 91 and 180 and have never had a problem but I run 22:1 Fuel/Oil. I have not raised the C/R on my four stokes but I have on my two stroke conversions and the HP goes up with no adverse effects. All of my conversions are running fine and the Supertigre 90 gets used every weekend. Runs like a top and swings 14X6 lumber 9800 pulling my Goldberg Tiger 60 around nicely. I am using 16:1 Fuel/Oil in the two strokers.