I looked at the parallel thread on "
capsized stories" and there's something about the description of the capsize that seems useful to analyze:
spoke36 wrote: I misjudged a gust. ...I let go of the main and pushed on the tiller to point up but still had my jib cleated in a jam cleat. My DS1 ... turned over and the mast hit the bottom.
What happens if you suddenly let go only the main is that you remove the force that allows the DS to round up, leaving just the jib, and that will want to turn the boat further downwind. At that point, you may not be able to steer into the wind because the force from the jib turning the boat downwind wins. Also, if you push your tiller at too big of an angle, you may stall the rudder, losing all steering and the boat will definitely not head into the wind.
I wonder if that is at the heart of the scenario in the cases where people report capsizing with just the jib.
A better strategy would therefore be to not throw the main sheet loose, but to let it out (controlled). The effect would be to depower the main, but, even though it is depowered, it would still contribute to balancing the boat, and retain some weather helm that would assist in steering into the wind. That, in turn would help to depower the jib, even if the jib is cleated.
When single handed, you may benefit from holding either the main or both main and jib on your hand at the same time; something I tend to do especially in gusty / shifty conditions. Even if my jib is cleated, I keep the sheet in my lap so if I need to, I can depower both w/o having to reach for the jib sheet.
If you fit ratchet blocks on both main and jib that makes holding them much easier.