I have a Seagull PC9 and was flying it with a Magnum 52 FS and it barely had enough power, would fly but was very difficult to do anything with. Then put a Thunder Tiger 54FS in the nose, was marginally better. Got tired of messing around with it and now have a Saito 72 FS at the front. Now it has some authority and flies like it should. I doubt if a 40LA will do anything other than taxi it on the ground. It sounds like your plane will be grossly underpowered to me.

My experience with these things tell me that unless you just want to do slow, make that very slow circuits with that motor there is barely enough power to pull it off the ground. I have another PC9 in the cupboard and would not fly it with anything less than a 46AX or the 72 Saito.

If I was a LA 40 engine in the front of a Seagull PC9 I think I would keep on stopping as well, not even nearly enough power to fly a low wing bird like that