I think there is some confusion here though hothead - it is not theoretically possible for a trans person to identify as a radical feminist, they hold totally different theoretical standpoints about what constitutes gender. If they say they are a radical feminist they are confused about what radical feminism is.
A good analogy might be if an atheist like Richard Dawkin suddenly said he wanted to attend a Catholic mass, take communion, because he really was a catholic at heart - and the catholics say "but you don't believe in God, you can't be a catholic" and he says "but being a catholic isn't about believing in god it's about having lovely services with uplifiting music, music is central to my life so I want to be a catholic "
I am a wishy washy liberal socialist feminist, not a radical feminist - so I too am excluded, by definition, from a conference for radical feminists in exactly the same way as I would be from a conference for catholics.
For a trans person to share the view of radical feminists on gender they would have to cease to be trans. Rad fems say gender is only a social construct, which means that it is potentially totally fluid depending on the context one is brought up in. Trans activists say that they have a sense of a core gender identity that is at odds with their biology.
So AIUI for Rad fems Gender = fluid for Trans Gender = fixed. For both of them it is the issue of gender which rattles their cages but they disagree at a very fundamental level.
Personally I think both positions are wrong and mine is right 