It sounds like you need a contrastier negative for contact printing on the paper you are using. In general, you can extend your development times. For this negative you can intensify it. I like to intensify in Kodak Rapid Selenium Toner, 1+3 for about 8 minutes to get about a one zone increase in contrast. For more, you might look into other kinds of intensifiers or bleach and redevelop methods.

That said, when I'm printing on VC paper, I usually expose for the white and adjust the contrast for the black. You might try that and see if that gives you a result that you like better. It might not give you maximum black for the paper, but maybe in this image the highlights are more important, and you'll have enough black that you'll be satisfied.