I have not owned a FOX gas engine but have seen several of them. Had hands on a couple. For the most part they are very similar to the Brison engines built with an in house made cantilever crank, purpose made case and Sachs based pistons and cylinders. All very good engines. As the cylinders are all from chainsaws, these engines (like Zenoah) usually make their power at a bit higher RPM than the newer purpose built, reed valve RC engines. Don't lug these engines with a huge diameter prop or you will be disappointed in their performance.

Its really all about application! if you are building something like a Zero or other short nosed warbird, these older piston ported engine designs are perfect with their short length. Its not so easy to stuff a rear intake engine into a Zero as the carb can end up behind the wing LE and inside the fuselage! Likewise, if building something like a Mustang, one of the newer rear intake, rear exhaust engines are perfect because they fit in the cowl w/o the need for any nasty extra holes, bumps or bulges on the cowl.