If I were going to switch to an 11 inch prop it would be 11x4; possibly 11x5. Using a free program called ThrustHP (do a Google search if you want to download it) it appears you'd gain about 2 pounds of static thrust at 12000 rpm by going up in diameter. I have read on RCU that the program is pretty optimistic about the numbers but it should at least be ok for comparison.

For 10x6 vs 11x4 @ 12000 the calculated numbers were 4.32 and 6.32 pounds. Even if the real numbers are more like 3.5 and 5.5 you still have an idea of the difference you might see.

Ideally you should check the rpm with the 10x6 and with the other props you try and plug in you actual numbers.