While the Magnum is a .50 (.5 cu. in.), the Fox 50 Gas is not .... This is from the 'front page' of the Fox Mfg. site:

"SPRING SALE ON FOX ENGINES

We're pleased to offer our famous Fox CL engines and Fox RC engines at super low prices and YES, this sale DOES include our NEW FOX 200cc Gas engine and our NEW FOX 50 Gas (12cc) Engine.

THIS SALE also offers FREE SHIPPING."

A 12 cc engine is a .78 cu. in. - so a little large for MOST control line, although I'm sure that there are some applications for it.

In trying to find out more about weight, fuel, price, or any other details, I spent a while poking about on the Fox site and can find NO other mention of this engine. So I don't know if it is actually available yet anyway.

As to what advantages this would offer, I'm also not sure. Probably somewhat lower fuel costs.