ORIGINAL: reaaz
a 60 sized engine was the desired engine of choice for allmost all rc aircraft in the earlier days of rc aeromodelling. Although aerobatics has evolved mush since then, the current 60 engines do quite well for standard aerobatics and loops in airframe sized for that class.
However don't expect them to hover... I had a K&B.61 baffle piston type engine. that flew standard aerobatics quite well on on of the older lanier foam & vacuformed plastic Plane I had.
There are a few similarities, but not many!
I was reminded of this a couple of weeks ago when a flying buddy showed up with an old Dirty Birdy that was well built and is still in excellent condition, powered by one of the old long-stroke .60's and weighing
at least 9 lbs and very likely somewhat over that.
The Dirty Birdy wing has a very thin airfoil (relative to today's aerobats and pattern ships) and the model really needs speed to fly, and must - and does! - carry a lot of speed into vertical segments. It must also be landed at a pretty hot pace compared to modern designs with comparatively light wing loadings.
Because of its much thicker wing and tail feather airfoils, the Phoenix Extra won't carry a lot of speed into vertical maneuvers and therefore needs more engine thrust to power through them. Also, because of the Extra's small fuse side area, it also needs a lot of power to hold a knife edge, and even then it takes a LOT of rudder deflection.