Yeah, a droopy hood can be a pain - never had the 105/2.5 AIS hood be a problem through. And yes you can get a nice reversible snap in hood, but I hate having extra stuff to keep track of, especially when up in the mountains. Built-ins never get lost, are more compact, and stay out of the way when I don't want them.
I actually use a Nikon snap-in hood for my 180/4 Voigt and it fits like a glove when reversed - and looks right at home with the chrome and black.