RE: Wanting a 4 stroke to replace current 2 stroke.
One thing I have noticed with the same plane ( seagull PC 9 ) . mine with a 70 os 4 stroke and a club member 45 supertigre is that his 45 would leave mine for dead. I also have a 82 saito on a 40 size stick and have had a 52 supertigre on it and the 2 stroke is faster again. These are just my observation so please dont shoot me [:-] Cheers the pope