has anyone heard or had problems running 2 in aluminum dually spacers?

Just be sure to get Hub-centric spacers. The center will have a flange that fits the center hole of the wheel(s), to help share the load. They (the spacers) will also snugly fit the the raised center in the middle of the hub.

http://www.dieselplace.com/forum/showthread.php?t=241307&highlight=broken+spacer