I think you would do better by fully releasing the downhaul and also (if you didn't do that) completely run out the main traveller even if that means that you have to pull the mainsheet in some. But releasing the downhaul can make a big effect.
The only problem is that if you release the downhaul completely, your mainsail can unhook at the top and come crashing down after righting. Hoisting and hooking the main back in can be a real pain when on the water. (I found out the hard way)
I use one of these to quickly disconnect the mainsheet from the sail/boom:
![[Linked Image]](http://www.wichard.com/catalogue/base/grandes_images/smoudrisseoeilfixe.jpg)
