2 slow, i certainly hope you are missing a zero in that rpm figure :-) Is that RPM reading for 15% or 30% nitro?

From the hip, I would say that that isn't enough prop for the engine. I would say you should run a 12 x 6 APC on 15% nitro. And 12 x 7 on 30% nitro. For a three blade prop, you can go one lower in pitch or diameter. In my experience APC props are much more efficient than MAS but don't look near scale.

Try the APC 12 x 6 first and the 12 x 7 second. You should still be able to get 10~11k on the tach. Remember, 11k on the tach would certainly go to 12k unloaded in the air... that is pretty much the limit (as per manufacturer's specifications).

Forgot to mention that should be around sea level at a nice flying temperature!