Mark, The speedbrake needs to be behind the center of gravity. The further it is from the cg, the more it will affect pitch, etc. It needs to be mounted securely, and the rear spar is the logical location, unless you like adding structural weight to accomplish this elsewhere.
I have an electrically actuated speed brake also: I wanted control close to the throttle with minimum hand effort during the critical time of landing. I am using the seat actuator from a 1985 GM car for my actuator (cost $15). I'm not flying yet, but this is the way I've set up of my speedbrake. Jim Vance va...@claflinwildcats.com
