Confession: Though I worked at Fox, I never saw an operating Fox .049. Sure wanted one, but never did get around to scrounging up the parts and fitting them/etc.
However, a friend that also worked at Fox long before, during, and after my years at Fox, told me the FAI .049 was indeed stout for its size. IF I'm recalling correctly, he indicated that most fliers tried to rev it like a TeeDee, but those that figured out it would swing a bigger prop than a TeeDee began to have the speed advantages over the TeeDee crowd using a prop that the FAI liked instead of trying to run it like a TeeDee.
Sorry, I can't remember what prop(s) he recommended.
Andre