I was wrong
So the last post I entered here was wrong! That would work for each individual gallery, but not for when creating new galleries. If you want a certain style to be your default style each time you create a gallery, in the power gallery database, edit the "structure" of the pg1_gallery table and set the default value for the design column to the name of whatever style you want to be the default. This will force the gallery to use that design when a new one is created.
Jason helped me with this, and I wanted to pass it on so it would be available to others.