Downside?
weight -
other than that - smoother running -especially at idle --
less fuel costs - huge difference-
no goof ball fuel induction system like the fool injection now being fobbed off as necessary .
I have been runing a 40 powered pattern plane all fall now and the engine has never once killed even at lowest idles - and power is way overkill- if the engine were say - 80% of what it is -weight/power -etc -it would be perfect for the present models.
I never had problems with the glow -I figured out what they needed -did it and away we went - BUT the cost of operation simply became a big sore point with me - $15.00 a day !
Now it actually costs more to drive the 30 mile round trip than fly all afternoon And the engine maintenance costs are ZERO No plug problems - no rebuild s - Am I sold ? absolutely .