Wow indeed.

I've messed with these RC things for 50 years now & I've owned & tested more engines than most of you guys have had years to live. An 11-6 is absolutely not the correct prop for either an OS .46 LA, or particularly an OS 40 LA. On 10% nitro & @ 400' asl, the 40 LA can't turn an 11-6 above ~ 10,300 - 10,400 static rpm -- the torque peak is @ 12,700 rpm & the power peak is @ 13,400 rpm (real world -- not OS advertising). The 11-6 will positively kill any acceleration & climb -- performance factors that you will need.

For a trainer aircraft, fit either the 40 or 46LA engine with an 11-4 -- the 40 will spin it @ ~ 12,000 & the 46 will get it up to a bit over 13,000, giving you essentially all of the power available from these rather weak engines. The cruising airspeed will be limited by the flat pitch prop (and the throttle -- that's what it is for), while the plane will be able to take-off & climb strongly (which I guarantee it wont do with an 11-6). Landing speed will also be significantly reduced with the 11-4 over that achieved with a high-pitch prop. At idle speed, the slipstream velocity from the 11-6 will be nearly 50% greater than that from the 11-4 & that translates directly into airspeed at idle -- which would be at landing. Additionally, when the throttle is closed in flight, the 11-4 acts as a much more effective airbrake than the 11-6, thus more rapidly slowing the airframe -- it will permit a steeper descent with the 11-4 at a safe airspeed -- which would be your landing approach.

And one more thing -- overloading the engine with an oversize prop will not only limit the output, it will cause the engine to run hotter & and wear faster than it would if correctly propped. It can cause detonation (pre-ignition), it increases the piston side load (rubbing on the sleeve), it increases the shear load on the crankpin & wrist-pin & it increases the radial thrust load on the crankshaft bushing. None of that is good for the engine. These little OS LA series engines are particularly susceptible to overload damage, as they have very thin cylinder liners. Non symetrical heating from side-load friction can cause local hot-spots on the liner --- which will eventually peel its nickel coating.