HOME: Suggestions for treehouse platform support without posts

I'm building a treehouse in a fully grown 50 foot tree that has four trunks (as it were) each of which is between a half foot to a foot in diameter. First, is this a good candidate for a small tree house (5x5 platform) that will be attached directly to the tree? If so, does anyone have any recommendations for supports in a configuration like that. I have some ideas but I wanted to get the opinions of people who have experience in contracting and even treehouse building.