Something you may want to consider is a quick release based on the Skydiving system. This system is very reliable and releases easily. It utilises a quick release pad ( to avoid accidental disconnects ) and can be activated from any attitude.

Here is a very detailed explanation http://www.dropzone.com/gear/articles/The3RingWhatItIsAndHowIt.shtml

I am very familiar with it and it has saved my skin on more than one occasion.