What can i say... i cant argue with the physics and torque curves between the 140 FI and say the YS 140, it would be futile. From my experience, the 140 FI is a very powerful engine and it makes in the range of 3.5 - 4.0 hp at full throttle, which should be ample to drag a 2 meter machine such as the Pro-line around, like Vellum says it does in his earlier sentiments. The only real disadvantage i can see with the OS when compared to the YS is the way the power is delivered versus throttle position. The power delivery of the OS relatively speaking is delivered in an non linear or exponential fashion where the 4 strokes is more linear. It does most certainly makes sense to make it easier on the guy piloting a pattern plane through a complicated sequence to make the power delivery linear, it makes power & speed control easy, which makes it easier to perfom a dificult sequence, which potentially translates to better scores. For those of us who dont have unlimited access to the latest and greeatest 4 stroke motors why cant you setup the throttle curve to deliver the power in a linear fashion...with some tinkering, this exactly what i have done. Now although the throttle servo has exponential programmed in to its travel, the power delivery is very linear and easy to anticipate.
With the power the 140 FI makes and with the throttle curve adjusted, i still fail to see why using this engine is not viable in a light model like the Pro-line. Given the model is a of the widebody variety, granted yes it does have higher parasite drag characteristics, but as the parasite drag curve itself increases exponentially with speed then the overall need to overcome that drag with the low flying speeds of this type of model should be relatively low.