I figured someone as Severus being so out of charachter would drive how dangerous the task was with more efficiency then if Sirius was the one having a fit, especially since he tends to overreact here. I mean, besides the trio, evryone in Canon was acting as if Harry facing a dragon was the same as Harry going to play soccer.

I don't know, sometimes I think Sirius had a lot of Slytherin qualities. He was loyal to his friends, and brave and most of all he wanted very badly to defy his family (as he let it clear in that memory in DH). But he was ruthless and he was very, very selfish in my opinion. He thought of himself and forgot how anything afected others (I think the prank and the fact that he went off after Pettigrew without a thought to Harry proves that). That doesn't mean he is a bad person, just not perfect, and who is after all? But my point is that putting oneself first always is quite the Slytherin quality. I don't think anyone can fit perfectly in only one house, and most people must have gotten more than one possibilitie when conversing with the hat. Remember, this is Sirius telling the story. The hat might have even thought Gryffindor best for him even if Sirius hadn't said anything, and just have mentioned Slytherin. Like it did with Hermione. And I could definetly see Remus in Revenclaw, I bet he got a little pondering too. But I thought Sirius, who wanted to be anywhere but Slytherin, and preferebly were the aneurism his parents would get would be stronger, wouldn't have even given the hat a chance to ponder and would start to argue for Gryffindor at once, and then off course remember that he was the one to convince the hat, even if the hat had shouted to the whole hall that it would have but Sirius in Gryffindor regardless.

But in the end I think the hat would have chosen Gryffindor, just as with Harry, because even if Sirius does have Slytherin qualities the Gryffindor ones are predominant. But I also think, that just as with Harry in the books to a younger Sirius, the hat having considered Slytherin might have been a great shame that he would keep a secret. But as you said, as an adult in my story he has grown, and can now admit that freely and even taunt Severus. I don't think canon adult Sirius would have.

Thanks for the input!