Behan, a cruising friend of ours, started a discussion on downwind sailing sails. Check the Totem's blog for details.
There are lots of different downwind sailing options. Here is what we do on Merlin (NB: usually without the main!).
You can check Greg's short video of our symetrical spinnaker set up on Merlin. That works so well. We crossed most of the Pacific with this system because it is easy, efficient and safe.
With this set up, there is no gybing stress, no mainsail chaffing, no mainsail reefing stress, just the wind pushing us along and the autopilot having an easy time keeping the boat on track. The quick release clip on the one side is the key as the person on watch could de-power the boat from the cockpit in only few seconds, then getting it down behind the genoa with a sock is so easy. We can go about 60 deg either way with the spinnaker still flying properly.
We love using our spinnaker as often as we can.