A longer acclimation would do nothing in regards to what a proper QT would do. QT with copper medication is just to take care of any ich it might be carrying, which hippo's seem to be super susceptible to.
If it makes you feel any better, my hippo usually gets ich with every stress or change that happens in the tank. Seems to be the same story with other peoples hippo's, you walk to fast near the tank and poof, your hippo looks like he swam through a blizzard. I have yet to get ich on any other tank member, ever, but he seems to always have some on him every few months/weeks for a day or two. My cleaner shrimp usually cleans him well though. Its only been recently when i did my tank move that he's gotten ich that hasn't gone away but he hasn't been hanging around my cleaner shrimp. Again, none of my other fish show signs of infection.
Just make sure you don't throw him into an overcrowded or small tank. Ive been lucky with the ich, but there have been new hippo's who've infected complete systems with ich before.