Requesting 'fluid' ad size for DFP/Ad Manager

[Stephen]

Is that not this?

AdSense Responsive Ads

IF YOU ARE RUNNING AN AD BLOCKER RIGHT NOW YOU WILL HAVE A VERY BAD TIME TRYING TO SET THIS UP! TURN IT OFF BEFORE PROCEEDING DOWN THIS PATH! You’ve been warned. Google AdSense offers the option to show ads with a size of Google’s choice using the responsive ad size option. Note that responsive ads are an all-or-nothing option. You can’t limit the height and width of them. They will cause jumpy behaviour when scrolling within a topic. It is recommended to use …

Or at least the right topic to be asking in?