I once owned this stem. Beautiful and saved grams but did give me some headaches. As already noted in this thread, Zipp bars slipped unless torqued above spec (properly fitted with paste). Result was stripped bolt heads after a few loosening/retightening of bolts. As you mention, I also had fitment challenges with Edge forks and had to sand down the steerer tube to get the stem to properly fit. Finally, if you are a sprinter, I would not classify this stem as stiff. All that said, stem is a gorgeous piece of kit, I just would not recommend it for a race bike application especially if one is a sprinter.
what may you recommend to those more suited to sprinters/actually sprinting, and often. (I'm still wanting to be a WW on the stem however, if possible) thanks in advance.