OK, it appears that the body text and the caption text are linked together within the theme so that if you change the body text font, the caption text font also changes. However, the the body text can be increased/decreased in size, but the caption font appears to be set at a fixed size. I didn’t like the look of the original body text font (Arimo) at a larger size, so I changed the font completely (Pontano Sans) and discovered that Pontana Sans looks good as the body text (at a larger size) and the caption text (at its fixed smaller size).
So, I basically found an acceptable solution for my needs at this point.
I appreciate your help!