The HolidayCoro ones stack, yeah, but it's a CPU board and then up to 3 output boards, then I suppose you could use another CPU board and more, if you really like towers of standoffs... but good luck changing some of the fuses if you did that. 16 ports per board, they aren't tiny. Or thin. The network bounces from board to board, so that's handy.Isn't that kinda similar to the boards Holiday Coro sells?