Resizing Player to Fit Powerpoint Content

I think when you go to publish the project, you can go to the other setting on the properties page. There you will find a small gear in the tool bar. Click to open the settings. Try clicking on the box " Launch player in new window (create launch page)." Then make sure "Browser size: " is set to "Resize browser to optimal size."

That would be my first choice. 

Also, I know I had issues with changing the size after the slide were imported. Luckly, I had not gone far enough into the project to just dump it, resize my storyline and reimport. 

Good luck