PowerPoint Import

When I import a PowerPoint file into Storyline 2 update 7, Storyline is changing the font size of text .  In PowerPoint the slide master placeholder is set to Arial 18, but when the slide is brought into Storyline that text is changed to Arial 13.5. Fixed text on the master slide, as opposed to a placeholder, is not changed.  This also occurs with any text placed directly on the PowerPoint slide (text that is not fixed on a slide master).  Even the master slide that is imported to Storyline is changed in this way.  That is, the master is PowerPoint is set to Arial 18, but when it gets to Storyline the master is set to Arial 13.5.  Is there a way to prevent this?  We need to storyboard with SMEs in PowerPoint and then import the content into Storyline when finalized, but it is not good if the font sizes we standardize on are changed in this way, requiring us to touch every slide and/or master after it gets into Storyline.