Well....don't have experience with the 5000-series collators (I am familiar with the DC-10000-series), but a 4-page sig should feed fine through that system into the bookletmaker. The main issue will be the disproportionate pile height bewteen the folded side and the loose side. You will likely have to put a small stack in the bin(s), keeping sure the folded side is as flat as possible. You will likely have to turn OFF the doubles detector because of its thickness.
You should also try contacting DUPLO Tech Support(!) if you haven't already.