Here's how the unicorn handles a magic body part. This is tacked on to the Combat description: "The horn is a +3 magic weapon, though its power fades if removed from the unicorn." Overcoming DR/magic is implied in this case.
How's this for staterts?
"Speed Glide" (Ex): When moving its full base land speed, a tybor floats several inches off the ground. This allows the tybor to move unhindered through slick or dangerous terrain. The tybor may even run over the surface of water. This ability lasts while the tybor continues to move at its full base land speed and for 1 round thereafter.
Based on what GrayLinnor posted for the stats, I like: Str 14, Dex 18+, Con 15, Int 18, Wis 18-19, Cha 19.