Fox was our choice for A class engines for many years. I say "was" for the very reason Cajun mentions...durability. Mid-airs and dirt naps took the muffler and carb bosses off way too easily. Once Magnum came up with a good .15, that also prooved to be MUCH tougher in crashes, the FOX's were scrapped. I still have one, and it's a screamer...but not for combat.