Getting back to the original question ---yes you can improve its performance noticeably with a different prop.

Try an APC 11-5, or 11-6 -- either one is a good all-around choice. An APC 12-4 is also good -- you will get very good acceleration & climb & still get decent top speed.

An 11-7 is a bit too much for that engine to give peak performance, an 11-4 will give spectacular acceleration but you will need to run at part throttle in level flight, a 10-6 or 9.5-8 will give good speed but are much too small to give decent all-around performance (DR-1 noted that). The 9.5-8 is a particularly poor all-around choice -- while it will make the model go fast, it will make take-off very sluggish, give very poor emergency throttle response & raise the landing speed substantially.


My starting choice would be an APC 11-5 -- good speed, good climb & acceleration, reasonable deceleration & slow idle-discharge-velocity, which translates to an acceptable touch-down speed.