it would seem that you want to suppress the new page before...I am assuming that is the mechanism that is 'wasting' space. There isn't a way to predict how many pages any given data will hold, and you haven't mentioned what sort of layout the user desires....if they just want to reduce paper waste, I would do away with any forced page breaks and see how the data lays out.
Subreports would seem to be a red herring for the above reasons...you don't know how much room they will take, they will be accessing the same data but in a less efficient manner as it will multiply the number of hits to the database.
HTH