can i swap the digital outputs on HD 8x8x8

i just bought the HD 8x8x8 to add more I/O to my Omni , i would like in the future to have 16 instead of 8 I/O's....can i swap the digital expansion board on the 3rd expansion bay with an analog input ? or is it a default and i can only add a board on the free expansion bay?





thx