it took me 3 tries but I got a door that is nearly leak proof, in the future I will use the cut out to make my doors and then add the inner frame like bobhenry showed. with that and an eyebrow above the door, even if the door warps there won't be a leak.
I built my doors using the same method I built my sidewalls
gallery/album.php?album_id=3189
the only thing I would add for the next build is a outward sloping bevel to the top of the door and an outward sloping bevel to the bottom of the door hole in the tear. Gravity and surface tension do the real work.
each door took a few hours over a few days, mostly because of drying time for the glue.