It is hit and miss, although usually more hit than miss (just not 100% for everyone). Adding that the AICS magazines tend to work even better than the double stack stuff. For example: I have two AI AT/AT-X magazines with different followers, and both will nose dive 6GT rounds about 5-10% of the time in my AT-X.
My work-around at the moment is to just load the rounds forward in the magazine. It seems to work fine (so far) from static positions, but I'm pretty sure that it isn't a solid fix once I start running around and letting the rounds move inside the magazine. Neither magazine has ever had a hiccup with 6 or 6.5 CM.