Jeff,

A Nelson won't do the job for aerobatic because they don't make them, but there are Jett engines that are tuned for low rpm high torgue that can swing big prop. However, a .40-.50 engine for aerobatic plane may not be the right choice for your application. Probably best to use a YS .63 for that size range. Although a Jett .50 will out perform a YS .63 any given day of the week, but it's not the right choice because it will fly your plane too fast, which defeating the purpose for aerobatic flying.

Yes. A Nelson engine were strickly made for racing application, but not all Jett engines are. Dub Jett does make racing engine, but majority of his engine are for sport use and are sold to Sport Flyers. Most people think because he makes racing engine that all of his engines are for racing only, NOT true! However, there are many benefits to buy a Sport Jett engine because it derived from proven records from racing into sport. Like the automotive world from the race track to the street.

Here's an example for those that believe a 2 stroke are only for speed and can only swing itty bitty prop. Well, better think again...
A 2 stroke Jett .120 can swing a 16x8 prop around 9000 rpm and 15x8 around 11000 rpm and will idle at 1200 for the norm. Now, that's impressive! Now, would that one person think a 1.5hp 4 stroke fly better than a 3hp 2 stroke? Hmmm... think not!

Sorry to go of track, but my recommendation was based on your post for POWER, and if power was your main concern then by all mean the Jett engine fits it like a glove. There was never anything mention for aerobatic application.

Sam