I might have a solution for you (and anyone else for that matter).
I wanted to to the same thing for my local threads and cooked up a Yahoo pipe to do this:
The Thread ID is the number right after the t= in the thread when you click on the thread form the forum index.
What it does is it takes the forum thread and filters out everything else but the Thread ID specified.
In theory this should work, one thing I noticed is that the RSS feed is a little behind the real thing.
Let me know if it works out for you, ill be using it too so let me know if there is any problems I will fix them up for you.