same happens to me ! . if the plastic part( air brake) is properly instaled, i recomend you to aling i the trailing edge of the elevator with it , even if you have to put the leading edge of the elevator flush with the wing shelf.
on my firts fly i apply up elevator went i released , the plane goes down like a rocket ; i have to apply full up trim and still need a bit of more up. went i check the elevators , the trailing edge was about 1/16 over the the air brake.
im dont telling you that this is your case , just be carefull !! because those full flying stabs are very sensitive.

pecojets