🚀 go-pugleaf

I have two LaTeX problems that I could do with help on.

1) \underbrace in a \array environment
I would like to put a series of underbraces under items set out
in an array environment
   1   2   3   4   5   6   
       ---------
   ---------
           ---------
Without affecting the spacing.

2) I want to set \footnote on a table (\tabular) in a \minipage
so that the width of the footnote width is just less than the width of
the table.  Obviously the width of the table is known after it is set
but is this to late to pass to the footnote?  If it is could it be
passed for use in the next pass of LaTeX.

\centering
\begin{minipage}{\textwidth -  fix}  % fix is initially zero on the first
\begin{tabular}{ccc}                 % pass but is written to the .aux
  &   .......                        % file after it is calculated as
\footnote{set this at the bottom}    % \textwidth - tablewidth = fix
\end{tabular}	                     % Must be associated with the
\end{minipage}                       % appropriate table

Unfortunately I do not have the skills to program this myself.