Wow Stefan, your Evo must have 9 lives! Could be an interesting project!
I guess your best bet is Ola as he has been thinking about converting His E70 2007 into a twinfin/thruster set up. If he hasn't allready done that he might have at least some ideas.
Another good read is this thread on the boards.co.uk forum, where chrispavlo converted and Acid into a Twinfin: http://www.boards.co.uk/forum/forum_...ion&PN=0&TPN=3
Good luck with the broken foot.