Hi, an idea plagiarised from polysquare http://www.thingiverse.com/thing:1858501 but for the v2.1 which has an extra stiffening ridge in the base plate.
I used Inventor for this. Prints very well. I used a raft, but probably didn't need too.

quick update: I originally used PLA for this but have been printing a lot with ABS, some long time prints at that. I have found that this has been effected by the heat of the 90deg bed and has dropped to the point where it now catches on the frame. I suggest printing in ABS and using a thin adhesive tape, not a foam backed one, like I originally have.

Hope that helps