When i say up thrust that would be angling the tube exit up so as to create a downward force on the tail. This would counteract the high thrust line somewhat and would reduce the airspeed the plane would rotate at making the takeoff distance much shorter and would reduce the pitch down tendency when throttle is applied. I could care less where the trim ends up but would want to minimize abrupt pitch changes with throttle and to shorten the takeoff. The smaller sky master bd jets i have seen seem like they are up to flying speed in 150 feet but cant rotate until the plane is400 feet down the runway or if the pilot panics and chops the throttle they will suddenly jump off and go oops.... How much room do you need to takeoff?