ORIGINAL: Pilot Chad
If you do get the UCD, get the 91FX instead of the 61fx, it has more power and is lighter, just have to prop it correctly so it doesn't go to fast.
You may want to check you facts and possibly rephrase your advice. The 91 FX IS NOT lighter than the 61 FX. In fact, they are the same exact weight. Go to OS engines website [link=http://www.osengines.com/engines/power-chart.html]OS engines power chart[/link] both weigh 19.42 oz. The 91 FX does have more power, but it weighs the same as the 61 FX.
Ken