Charles,  regarding your problem of straightening the bottom board in
the Regina disk cabinet, I have a couple more suggestions.

If you decide to replace the crooked board, this might help.  After
you remove the board, place it bottom (convex) side up on the table
saw and cut off a 1/2-inch strip along the back edge.  Then tack or
staple it to the edge of the new board to act as a cutting guide.

If you want to try to straighten the board, leave the assembly whole
and place it upside down (as in the pictures you sent).  Place
something heavy (50+ pounds) on the hump and leave it like that for
a few weeks.

You might want to spritz a little water on the concave side of the
board now and then to help it along.  Get it good and wet and wrap the
bottom in Saran wrap.  You could even wet a paper towel and put it on
the wood where the warp is to hurry things along.  Remove any finish
on that side first.

If it were me, I'd just make a new board.

Have fun,
Craig Smith