I don't think 90's would work on an MCW60 setup, I dont think they would reach over the top of the cards. You could use the 45's Juggalo posted (the first link) and angle them to the sides (exit parallel with the card) and then link these with tubing. Put some good anti-kink coils on it (primochill are very rigid but still flex enough to let you maneuver them how you want) and you should be set. You could probably make this look very interesting and unique.