Hey kris42 -
Sorry, I don't really get over to this forum very much. There is a very active support forum for 2010 Weaver at http://wpweaver.info/forum .
But to answer you specific question, no. There is no way to make it a fluid theme. You can change the width to another fixed value. This is very much due to the decision to support several arrangements of sidebars, which require calculations based on a known width.
I will try to add a link to the support site on the Weaver control panel so it will be easier to find.