I have aluminum banjo fittings on my turbo, the anodizing is heat faded but they did not melt. I too have a good thermal siphon. I think that is something that is commonly overlooked when installing a turbo. The steel is a helluva lot cheaper though.
I could not find a -10 bender that would do a tight radius and allow me to make a hardline turbo drain that way. I ended up purchasing a -10 adapter to bolt to the bottom on the turbo then bought a -10 fitting with the pipe coming out of it and welded the flex joint from the stock turbo drain to it and modified a few other things as well. It was a PITA, especially with the engine in the car. I may remake it so it is a bit cleaner than what I have.
I am interested to see what you come up with.
Here is a pic to show what I am talking about. Hope you don't mind me posting it here...
