Order posts by "best answer"

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I'm developing my board on MyBB 1.6.8 and I've installed MySupport 0.4.2 by MattRogowski.

All is working fine, but I'd like to build up with the help of XThreads and Pluginlibrary some forums with a stackoverflow.com-style: the main thing I would like to have is "order by: votes, best answer, normal" buttons and "best answer" set as default, so if an user post his question and then he marks an answer as best, it will be put on top, after first message. It's a intelligent way of building up support forums and I hope you will help me obtaining this target.