Best not to do that. The voltage from a fully charged 2S battery will be at 8.4V or higher.
Where do you think 7.4v as a battery specification comes from? Which battery is 7.4v specified? Right, it is a 2S LiPo/Li-Ion battery where the nominal voltage of a cell is determined at 3.7v. So yes, if electronics are specified for 7.4v then they wil work on a full charged 2S LiPo.