Looks amazing! I'm planning on building an led light with XML U2s and was wondering how hot they were going to get. Thanks for posing your experiences with them!!
Thanks. I really enjoyed making this light. Everything fell into place very nicely. Ultimately, I don't think the LEDs are getting too hot (since I can touch the aluminum without discomfort when there is not fan). Still, the spec says that the LED will last indefinitely when kept at 30 deg Celsius so I'm using a fan across them. I don't know, I will probably replace these lights sooner than before the LEDs wear out.