RE: New Fox engines?
I have a couple of Fox .50s that I've been flying since the 1980s too. I agree that the QC on the lo-spd needles left something to be desired. I used to buy several lo-spd needles from Fox and switch them into the carb until I found one that didn't let the engine load up in the mid-range. Another trick was to put a piece of fuel tubing on the needles, overlapping the spray bar, so that air didn't get sucked in while running.
CR