For more information about him and discussions regarding his work along with examples (some of which I present below), you can link here, here, here, here and here.
I get the impression that Willis might have been a bit more interested in his pinup's faces, rather than their bodies. That's because he sometimes painted heads that are too large compared to the rest of the body. You can check this if you're interested by Googling on Willis and then clicking on Images.
Here are examples of Fritz Willis' illustration art, mostly of the rare, non-pinup variety.
UPDATE: A reader reports that this illustration is from the Saturday Evening Post story "The Airborne Female," in a December 1956 issue.