I previously asked a question about using two different sans serifs, but I don't want that to turn into a "don't pair two sans serif" argument, so I'll try to come at it from a different angle.
I'm designing a book layout for an industrial design portfolio. I'm going for a modern appearance. I want to use a thick geometric sans serif like Gotham Ultra for headings, and either Mercury or Miller for body copy such as multiple paragraphs of text. My problem is what to use for a collection of only a few sentences? I like the look of a sans serif, but gotham doesn't look appropriate. Do I use a different sans serif all together that works for headings and body copy? Do I keep Gotham and use the serif anyways? Do I just use gotham for body copy? Or is it acceptable to use a second sans serif such as Benton Sans or Whitney as long as I keep the headings in all caps?