We're doing a one day hopper to Universal / IOA on our next trip too. It's in December, though, the week before Christmas week with crowd level predictions of a 3 and 4 for the two parks. I subscribed to the Unofficial Guide ($4 upgrade from my Disney subscription) to look at their descriptions of Universal stuff and their touring plans/most recommended attractions, and ultimately created my own customized touring plan (morning at Universal and afternoon at IOA after lunch at City Walk to see what we can probably get in, and it looks great to me.) We are (blasphemy on this board) not huge fans of most of the Universal / IOA attractions, so are mostly interested in the HP stuff and a handful of other things, and on these dates it looks like we can really and truly get everything we want to do in comfortably with room to spare. Our best bet appeared to do the Universal HP stuff at rope drop and the IOA HP stuff later in the day for shortest wait times with the other things we will throw in, in between. Can't wait and I think one day will be perfect for us.