Since I'm the Special Ops guy that did the review, I'll answer a couple of questions.
That thread was written before we had a chance to actually use it in the field. When we did finally get out and play with it, we loved it. Neither of us noticed any issues with double feeding or such. A little bit of background since we are not well known here (or known at all). We (Doubleshot is my wife) and I play almost exclusively pump anymore and mostly stock class. We were looking to build open class Phantoms for use in scenarios and larger rec games. When we wrote that review, we were not trying to be all inclusive with the other ways to mount hoppers to the center feed breech. We were concerned about trying to stretch the Winchester hopper (b/c we felt that the neck of the hopper was too thin). We did try the Ego feed neck, however we were not trying to do permnant alterations to the breech since we might be selling it. We used the straight feed neck b/c it's the one that available in any pro store and the kind of equipment that someone who isn't into trying to permnantly modify their equipment would buy to use. That's all. We do intent to aquire another PMP adapter for our other Phantom.