As above:
F20 is a bit much, I've only ever gone beyond f11 when it's been required to drop my shutter speed.
Which brings me on to 1/40 is 'hand holdable' with a wide lens, but I'd only ever settle for it as a necessity. I have my camera set to not drop below 1/250 so I don't have to worry about camera movement.
The other thing is, even when shooting for a large DoF, focus still matters. I would always focus on the 'subject' even if I was after front to back sharpness. Because the plane of focus is always the only thing 'critically sharp'.