I've got two hi-caps by different makes and neither work properly. At some point the spring just unwinds completely with a whizing sound. There has to be a lot of tension on the spring to feed all the BBs and the mechanism design just isn't strong enough to hold it. As you know, its not possible to wind as you play.
I have more success with the STANAG adaptor but I use short (20rnd) Vietnam hi cap mag which is much more compact. Using the wheel on that as I play works fine. You do have to roll the gun left and right a bit to get the BBs to feed into the side mag.