I think it's easier to duck dive a large face than it is to duck dive a whitewater avalanche. Easier to penetrate the water and hold on.
Anything under 3 ft barely requires duck diving at all, especially if you're on a board larger than 7 ft.
I'm 5'8", 160lb and regularly duck dive a 7'4 and 6'9 funboard. It is hard and on days I anticipate a lot of duckdiving I switch to my 6'6 thruster. A few tips that helped me out.
1. Time your duckdive. Don't sit there waiting for the wave to hit you, it'll wash you in and you've got to make up that ground you just lost. Nothing worse than burning out in the impact zone and having to take the walk of shame back up the beach. When you see a wave coming, start paddling toward it immediatedly. The momentum you build up translates into easier penetration. When I played football I learned something about getting hit. If you are standing still and another player is flying full speed into you, you absorb all the impact. You'll end up with the wind knocked out of you and when the stars clear, picking the grass out of your teeth. If you charge full speed into the impending collision, you actually divide the impact and as a result, often stay on your feet and end up with less injuries. Also, like football, hit it low. Take em out at the knees. Duck dive a split second before your hit by hitting the wave low. When you've decided you must duckdive a wave, charge it.
2. Use good form. Sink your nose too deep with your tail sticking out, the whitewash will just push you back by the exposed tail. When your momentum is up grab your rails right about the spot your shoulders line up. Do a push up so the only contact with your board is your hands on the rails and your toes on the tail. If your board is short, it's okay to have your butt pointed in the air. From here you begin your penetration into the water. I do this by pushing the nose down with my shortboard or pushing one rail then the other repeatedly with my funboard. Put your whole body weight into this "digging" operation my lifting one of your legs into a scorpion like counter balancing motion. The higher you lift this scorpion leg, the deeper your penetration will be. Once you've penetrated the water, flatten out close to the board and prepare to shoot out the back of the wave. There's a good animation of proper duck dive form at the 808 Surfer website:
http://www.808surfer.com/forum/viewtopic.php?t=246
The beach break where I surf, theres not much time to catch your breath before you have to do another duck dive, so once you've breached the surface, start paddling up to momentum again. We've all been in surf where we had to duck dive 15 times in a row, look back at the beach and realize we haven't made any progress. If you are in that situation, it's best to go back to the beach and reassess where you should paddle out. Look for a rip. If you find a good one, you can make it out to the lineup with dry hair.
Its hard for me to duck dive in 3-4 foot ( regular scale) waves, I cant imagine 5 foot waves (Hawaiian scale) 
