To maintain a smaller prop like 13" size on a 10lb-12lb plane and provide awesome performance, you need a high Kv motor capable of turning high RPMs/v and peaks of 1500w-2000w power output.

One such motor is the [link=http://www.hobby-lobby.com/actro-32.htm]Actro 32-3[/link] at Hobby Lobby.

I recently did a similar hop-up to my 9lb Lil Toni Racer from Great Planes. I decided to swap out the entire power system with new components that could easily handle a 2000 watt power level. The new [link=http://www.fmadirect.com/new_applications/BPHDSplashPG/index.htm]BalancePro HD[/link] (formerly Skyvolt) system from FMA Direct provided the ultimate Lithium pack operation and safety needed for this high-performance aircraft. The 6s2p BalancePro HD 6400mAh pack weighs 39oz. and can deliver 2100 watt power levels without any stress, excessive heat, or loss of longevity. When using the BalancePro HD 6s charger and Discharge Protection Module (DPM), every cell of my Lithium pack is protected during charge or discharge. The DPM connection is made inside the fuselage but the final DPM-to-ESC connection using the Dean’s Ultra plug is made externally under the fuselage after the wing has been installed.

Note that a 6s1p Kokam 3200 pack will also work here but the lighter weight also has shorter flight times and less top end power. You'll need to adjust the prop for a 60amp peak current level.

The existing motor was changed to a an Actro 32-3 outrunner. Using the same 14x7 e-prop as before, the current now measured 104amps at 2200 watts. That was 244w/lb.! The new Phoenix HV 85 ESC provided great throttle control and was an over-kill for the 2200 watt application since it is capable of handling up to 4000 watts (or 5h.p.). Note that a [link=http://www.hobby-lobby.com/jetiblue.htm]Jeti 90-amp[/link] ESC will also work well. For the Seawind, the prop can be changed to a smaller 13x8 size and maintain a full throttle setting at around 1500 watts. A nice 12" 3-blade like the [link=http://www.hobby-lobby.com/grprop.htm]Graupner Super Props[/link] would look great on this model and provide similar performance to the 13" prop.

Good luck!