I have to add my two cents, better yet, my two Fox 40's. After almost 9 hours engine run time on one, it finally runs sorta ok. The other has about 4 hours run time. I has very little needle valve adjustment tolerance. Tends to run too lean, or too rich. If rich, it richens further and quits when inverted. (I have a LOT of practice at inverted landings.) I put Randy Smith needle valves in both trying to "tame" the engine runs.
On the other hand, I have 4 OS 46 LA-S'. After 30 minutes to an hour run time, they are VERY reliable and run great. The only reason I still have the Fox's is that I can not in good conscience, sell them to someone who wants to use them in a stunter.