<font face="Arial, Verdana" size="2">Yes!!! That did work! Created a lower third graphic that is the same width as the screen, added the formatting tag:</font>
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<font face="Arial, Verdana" size="2"><img src="lower-third.jpg" width="1920px" style="opacity:0.75;"></font>
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<font face="Arial, Verdana" size="2">And then created a custom slide featuring just that formatting tag. Applied a transparent background to the custom slide, and it turned out exactly like I wanted it! Thanks so much for the great suggestion!</font>