Hello again,

So I decide to try with tables:

  \starttable[|m|m|m|m|m|m|m|m|m|]
    \NC \VL I\NC R\NC R^2\NC R^3\NC F\NC FR\NC FR^2\NC FR^3\AR
    \HL
    \NC I \VL I\NC R\NC R^2\NC R^3\NC F\NC FR\NC FR^2\NC FR^3\NR
    \NC R\VL R\NC R^2\NC R^3\NC I\NC FR\NC FR^2\NC FR^3\NC F\NR
    \NC R^2\VL R^2\NC R^3\NC I\NC R\NC FR^2\NC FR^3\NC F\NC FR\NR
    \NC R^3\VL R^3\NC I\NC R\NC R^2\NC FR^3\NC F\NC FR\NC FR^2\NR
    \NC F\VL F\NC FR^3\NC FR^2\NC FR\NC I\NC R^3\NC R^2\NC R\NR
    \NC FR\VL FR\NC F\NC FR^3\NC FR^2\NC R\NC I\NC R^3\NC R^2\NR
    \NC FR^2\VL FR^2\NC FR\NC F\NC FR^3\NC R^2\NC R\NC I\NC R^3\NR
    \NC FR^3\VL FR^3\NC FR^2\NC FR\NC F\NC R^3\NC R^2\NC R\NC I\NR
  \stoptable

This almost works, yet in the pdf output ("texexec"), there's an extra
column at the right full of "[missing column]".  What's going on here?

Actually, so far the best I've managed to do was to whip up a plain basic
array, and then insert two lines with TiKZ.  Clumsy, but so far it's the
only thing I've got to work...

-Alasdair