Grading of EJU Essay Section

I'll be taking the Japanese section of the EJU (窶愿ｺ窶怒窶板ｯﾅ?wﾅｽﾅｽﾅ陳ｱﾂ） this coming weekend in Tokyo, and I was wondering if anyone had any advice concerning the importance of kanji in the essay section. I've taken the tests from previous years, and I'm rather confident about the general level of Japanese the test requires, however, as a side affect of learning Japanese almost entirely through immersion and with very (almost no) actual classroom learning, my spoken / read / heard Japanese is much stronger than my written kanji.
The rubric for the test on their site says nothing about kanji in the essay, and instead focuses entirely on the logic and form of the essay, but it seems improbable that they are not judging use of kanji at all. How much would it hurt an otherwise perfect essay with a high level of vocabulary if several words it included were written in hiragana, when kanji would be the norm?
Does anyone have experience / advice on the issue?