The only advice I've heard is "thoroughly". That's a lot of meat, and a lot of layers. Heat has to get all the way through and be held high enough, long enough, to cook the innermost layer.(I've also been told that the result really isn't as good as cooking the birds separately. It's a classic feast item because it's hard to do well and is surprising, not because it's particularly good.)
Select as Best AnswerUndo Best Answer
kachun's turducken Instructable has a really nice set of links at the bottom, so he may have answered this already! Maybe he's even active enough to answer a PM.
Treat it like a tur-key of an equivalent size. You can easily find turkey-fry instructions. L