The rpm you are getting is about right. To test for correct length, pick up a bigger prop than you are now running, say a 12x11. Run each of them and see how the engine behaves. If you are too long for your current prop, the bigger prop will still needle and run OK. If it's fussy your current prop should be about right. Another way to tell if you are too long is if the engine richens up in level flight after taking off. If too short, the engine will lean out when you pull vertical.

Good Flying!