My first plane-trainer was a spad debonair .The total weight including engine and all was 10 lbs even. The 40 la couldnt take it off the ground untill i removed the buffle in mufler.Then after while as engine broke in and freed up a little more it started flying the plane.I could do loops,rolls(they were awfully slow) and stall turns but just. Then after while engine started loading up on a low side ,probably because the vent hole partially cloged up with grass and trash.I drilled it out a litle larger and it started working like a clock again.Anyhow,depends on what you like.You like take off vertical-40 la is not an option..You like to fly slow,more like a glider then you'll be ok.HOpe it helps.
Mitty