XSL-FO column width

I am trying to create a table with 2 columns and EXACT sizes, like:

<fo:table table-layout="fixed">
      <fo:table-column column-width="2in" background-color="yellow"/>
      <fo:table-column column-width="3in" background-color="green"/>
      <fo:table-body>
        <fo:table-row>
          <fo:table-cell display-align="before"><fo:block>Cell
1.</fo:block></fo:table-cell>
          <fo:table-cell display-align="after"><fo:block>Cell
2</fo:block></fo:table-cell>
        </fo:table-row>
      </fo:table-body>
    </fo:table>

The file is processed ok by Fop and another xsl-fo processor that I tried
here, but when I print the PDF and measure the columns, I never get the 2in
and 3in that I want, no matter what I do. I tried changing printers, page
size, etcb& and always get something like 2.4in and 3.5in. Can anyone help me
with that?

Thanks,

Alex