I am having the same exact problem as Pault. Using the recomended Satio 72. The distance off the firewall must near 4 3/4 and not 4 1/2 as the manual states. The engine mounts that come with the plane are bent. Horizon Hobby shipped me another pair and they are bent also. I am prob. going to order the Saito mount for the 72 (RR) and make more holes in the firewall. Not that I want to. The distance that the Satio mount brings the engine flywheel out to is 120 mm or 4.724". This should clear the cowl face.