I have : <itemgra item_types="highway_city,highway_land,street_4_cit y,street_4_land,street_n_lanes" order="10-18">
<text text_size="8"/>
to set text size. I believe there are limits to what it responds to, but try playing with it.

found todays svn works much better.. at least it's not immediately crashed when calculating a route.