Now the only issues I have had with a cold rich running (breaking in) was on one of my 6.5 cc Pylon engine and a 13cc Picco 80
<font color="#000000">Ducted fan</font> engines. I had set these up so tight that I needed heat the cylinder very fast with a flame to be able to turn over the engine. These engines failed the rods not the P&L fit (well not what I could measure after the rods let go).
While the P&L fit may suffer from running very rich on a highly tapered engine, I have been told that it was broken rods that made manufactures recommend tha the engines not be four stroked during break in years, no decades ago. The engine liner grabbing the piston as it cools off causes the rod to break.