Duplicating Item with villagers, hoppers and nether portal!

If you take 30 (or more) villagers, put next to 4 hopper system (6 hoppers connected to themselfs), and fill one system (theres 4, one of them 1 you'll fill) with a stack of any item. When you did, take the item you want to duplicate, and put on the other systems (other 3 parts), and leave them there. Then all you need to do is AFK on the nether portal, so you build a nether afk machine. That was made, and I made it and I really duplicated on survival. IT IS POSSIBLE, AND IT TAKES OFF THE FUN OF SURVIVAL! Please, fix it. I can send screenshots, but wont help so much. If you want, test it by yourself, any question, just reply this (sorry about the bad english, I'm from Brazil).