In the eyes of Islam, it is haraam to increase your wealth without any effort. As I can say for example you put some money to a man and from that money If you are given more money then it is completely haram. I mean, as you put some money at interest, the money that you get in addition to your honor is completely haram. সেই অনুপাতে Since you will be stacking then I would say that it is haram in the eyes of Islam if your capital is increasing through stacking.