Hi suzonka
You did not mention how far away the fuel tank is. On my Canard the center of the fuel tank was about 15 inches away from the carburator. I was getting irratic RPM during various manuevers. I added a 2 once fuel tank right next to the engine and solved all fuel problems. Muffler pressure connects to the main tank; main tank outlet connects to small tank pressure connection; small tank outlet connects to carburator. Your .25 engine, if in good condition and tuned right should handle a plane that size. I have a pusher puller with two .28 magnum engines. In the winter I can take off with just one engine, front or back. I use 9 x 6 props made by APC. The pusher prop is marked 9 X 6P. The P is for pusher. Make certain your pusher prop is not mounted backward. The efficiency drops tremendously. Let me know how it goes.