Saito cylinders being made from one piece aluminum alloy with no sleeve, then hard chrome plated, they need to be honed true, as there is very little wear on the cylinder walls, those radial marks on the ring face carries oil to help lubricate the ring as it gets pressed into the cylinder wall from combustion pressures, prevents galling of the cylinder wall during the bed in process... they incorporate a lot of design / manufacturing processes from the auto industry... for the most part they are a well designed and manufactured engine... I just dislike their integral valve seat design.

OS's rings are hard; that and with the hardened sleeve, takes a long time to bed in... not suprised, bowmen's process for making rings surpasses most model engine rings mfg'ers, they have tighter tolerances and fit the cylinder more precisely, which requires less bed in time... and like you mentioned they use ductile iron, properly tempered.