Forgot to say, I installed a piece of "Z flashing" in between the sheetrock and the hardiepanel. It should direct any liquid from above to get down into the trench, and not rot the 2x6 framing.
But yeah, having good drainage is good while brewing, Dert! I have had some boil overs due to guests not watching the tun (and a few while brewing solo), and washing it all down the drain is the EZ way to go.
More updates when I get stuff done.