Instead of using an "extra" head, you could do this:
Put your main css/js declaration inside a block in your base.html:
{% block headstuff %} blabla {% endblock %}
In templates that extend base.html and you want to add to this, do as
follows:
{% block headstuff %} {{block.super}} more bla {% endblock %}
The rendered block will contact "blabla more bla".
Good luck,
Erwin