Balsa Brain,

If the OS .30'syou have are plain bearing engines, you probably do not want to run one of them with a pusher prop. In that mode the thrust washer will be riding on the crankcase front end. Same reason manufacturers recommend not using an electric starter on plainbearing engines. BTW I have two of these same engines on a C/L deHavilland Hornet. They are not super powerhouses, but they are easy to start and extremely reliable.