Yeah, we developed IBoxes for the 05, 06, 250-1, 260, and 450. The 05 is the smallest program memory-wise of all those, so percentage-wise, you will burn more ladder memory.
Actually, what you are doing is a great implementation. Use the Success and Error bits from the IBox within a Stage program, and move to the next "normal" stage on success, or to an "error" stage on error.
However, make sure you get DONE before jumping out of the stage that has a Network IBox, otherwise you can leave the IBox in a strange state if you jump out of its stage before the IBox detects completion.