On the website it says 1.5 4cycle. So, i don't believe it is overkill. I also own 2 of the 100's, love em. Dimensionaly, it is a 1.20 size airplane, and the 1.50 is only 3 tenths of a horsepower more then a 1.20, and the physical dimensions are the same. Who makes the 109 you have? kit or arf? looks good

RAM-bro KMP Website is WWW.KMP.CA, all your pricing and dimensions are on that site