Harry, cobblestone generators have nothing to do with this redstone contraption and honestly I find cobblestone generators are ok in my opinion its just the dangers of lava and the exploits of pistons and thats why they aren't allowed and wkas, minecarts are the only thing I can use without worrying about people exploiting my redstone contraption for personal gain. I can't rely on the honor system since we get alot of new players and as you know you can never truly trust someone you met online. Minecarts are a secure method I find since they won't be able to cheat the vending machine. If there was a redstone device that detected block ID's, then I would probably implement something like that, but there isn't so I am forced to resort to minecarts. Anyways, as of now I'm working on the vending machine trying to make a counter that counts up and down so in case people accidentally put in a coin they can get a refund however this is gonna take time as I need to make sure my contraption can't be exploited.