Bob,
The board is about the same size as your PLC. This is what I could find:
Dimension: .5.0"(L)x 4.5"(W) x 0.8"(H)
Same size as T100MD1616+ -- allow stacking.
Please be aware that there is some orientation restrictions about how the board is to be mounted. There is some issue with the relays and heat buildup. I suspect that the plastic relay case may get soft and distort.
Gary d