Todd,
I operate the boat in one of 3 modes. first is full power mode in lighter winds ie only enough downhaul to obtain max draft and shape.
The second is in double trapeeze, but not overpowered mode. In this case the downhaul is played tokeep the boat flat. bigger puffs might require easing the traveler or mainsheet also.

The third mode is big wind mode. above about 15-18 knots steady, the downhaul is on hard and is never eased. I use a 16:1 downhaul and crank it on until the top of the sail is board flat and the leach flutters between the first and second batten. This is serious downhaul. Usualy female crews need to use both hands and pump with their legs when they pull in on it. A strong male crew can usualy downhaul harder then needed so I have them stop when the sail is flat and the leach flutters.

I would note that if you are going to use this much downhaul You are going to be buying mainsails alot more often if you sail in heavy air with any frequency.

It should also be noted that the jib downhaul should mirror that of the main, eased in light conditions, on hard in heavy air.

Sail fast, Take chances

Eric