What I do, when I want to keep the gimbal aimed upward is put slight pressure on the gimbal control wheel.  This will keep the gimbal aimed up.  However on long flights, I just let it drop back to center, as I don't want to put too much pressure on the gimbal during flight. 
It would be nice if it would drop smoothly as you mention it just jerks back down so a video would have to be edited. 
Paul C