I just put the finishing touches on the new D/H kiln yesterday. I'm going to fire it up today.I used plans that I bought the plans online from Daren Nelson. Daren has been building these D/H kilns since 2005 and offers his plans and email technical support for $25. I'll let you know how it works.
*UPDATE 05/17/13: The kiln has been running for a full day now. It's working like a dream! I've emptied 10 pints (20 cups) of water out of the drain bucket in 24hrs--Not bad! I would like to elaborate on the details here....temperature and such. But out of respect for Daren Nelson, who's design I used to build the system, I will refer any questions to him. If you are looking to build a small efficient kiln for yourself, Daren's plans are well worth the money. See the link to his site above.