skysfallin, I don't use those stock two piece engine mounts. I used a GP 40-70 mount for my Saito 82 for this plane. The GP mounts are sturdy and they have slots that allow you to move the engine up or down on the firewall (if mounting engine sideways). That helps to center the prop shaft in the cowl opening...gives you some room for error. With the Saito 82, my plane balances on the recommended CG perfectly. What I have been reading is that with OS and Magnums 91's the plane has been nose heavy. With the Saitos it seems to balance on or very close to the CG recommended. Jon