to Pearl 414,

The OS LA 40 and 46 are fine motors provided you don't want to do anything fancy, they are great on things like a Phoenix Classic or a Black Horse Twister. Never seen them called a sport engine, they are pretty basic. The OS 46ax or Thunder Tiger pro 46 are much more powerfull and versatile motors. With a low wing aircraft you don't have the floating characteristics of a high wing and need to pull them around with much more authority. I have seen the PC9 flown very nicely with an OS 46AX and a TT 46 Pro at the front.
My son flies the PC9 and he now has the power to fly inverted do loops rolls etc etc and the plane sounds like it means business. We are running a 13 x 8 prop on it and it really performs very well. With the 40la if you want something that can be thrown about a Black Horse Twister is well within the engine power rating @ 25 / 32 two stroke, we have one and had a 46LA in it and it went ok, now has a 52 magnum FS in it. I can't stress this enough read the instruction manual that comes with the engine and aircraft and operate within the manufacturers specifications and you won't go far wrong. The are lots of questions asked in this medium that don't need to be asked because all the answers are in the manuals. I can't see your PC9 lasting very long if you try to fly it with the LA40, you would need to lean the enging right out to get the power to get it off the ground and lean engines run hot and don't last long. Buy a Twister or a Classic and you will get a lot of fun and a reasonable life span for your motor