Hi Andreas, I have two different type score's and I know several people that fly them with smaller engines. I fly one with a Merco 61 lite case and the other with a K&B 61, both fly well. At first I was using an os 46 on one of them and was doing well, in some of the square manovers, the plane acted like it was out of air speed and dropped and guess, what totaled the fuseage. I rebuilt her using a magnum type fuseage.(wings and stab area wasn't hurt). I was using a merco 49 on my second one, did the same thing. I checked for wraps, miss alignment, cg, found nothing. Watched several other score's fly, flier said they loved the ship. After what happen to mine I watched as they when into the manovers and noticed their's had the same tendencies. Now that I'm using the bigger motors, doesn't seem to be there! The score looks great in the air seems to fly well. Probably just me but I would really be careful with running a smaller power plant. I know several people will tell you different and I'm sure they are right, its just what has happened to me. Good luck and have fun, Gary