From lack of response, I suspect that nobody has had much success with holding the string in the second joint. I would steer people away from doing this, and in fact am trying to steer one of my friends who asked me to teach him archery away from doing this, because it puts the string behind the reinforced part of his glove and I can see that he isn't getting a good release that way. He just seems to want to hold the string that way naturally and keeps coming back to it, so I guess I'll just leave him alone about it.
What you might try instead is one of the release aids, like the talon that is discussed a few posts down from this one. I don't have any experience with them, but you could PM one of the people who do and ask them about it.
OTOH, I don't have any experience with holding the string in my second joint either, and if you really like shooting that way, maybe you should keep doing it for a while and report back to us on how it went.