RE: Class A engine???
The Fora is a powerful .15, it's in the same class as the Cyclon I mentioned earlier. It will also set you back close to $200 by the time you get it set up, it aint' cheap, that's for sure.
The Gnat was designed for SSC (though it's not competitive against the current SSC planes), and is great in Gnat vs Gnat combat, where everyone has to deal with the same limitations. I'd guess that if guys are flying Gnat combat in your area, they probibly also have engine rules that are simular to SSC, or even more stringent. That would outlaw a Fora or a CV-A for that matter.
And, just as a thought, a Fora on a Gnat.... boggles the mind.