Van's kit does indeed mount in the elevator. However, I think it was Warren Gretz who came up with the idea of using a Ray Allen servo mounted on the aft deck between the horizontal stab halves connected to the trim tab using a flexible push-pull cable. These cables are commonly used in R/C airplanes (UAV's?). He even sold the cables for a while, I believe. That makes for an easy retrofit from manual trim. The only problem might be if you have a magnetometer mounted there.
