Originally Posted by
IAHtraveler
Never been an issue. Just approach with something along the lines of "I actually no longer need something that big. Can I just get the X in Space Y?"
Exactly. All else being equal, they'd rather put you in a smaller SUV, and then charge someone else for upgrading to the bigger one. Just remember, as IAHtraveler noted, that your needs changed. No reason to mention that you booked the tank because it was cheaper.