The engine is the altitude control, and elevators are the speed control. At least that's what they taught me in full scale flight school. Not strictly true in all cases of course, but in level flight , with the airplane trimmed to a certain power setting, yes. Climb and you slow down, descend and you speed up, or decrease power and descend, or increase power and climb.I don't use sidethrust, thats part of what the rudder is for. To me anyway, all downthrust does is change the wing and tail incidences relative to the thrustline. Ken Runestrand has a good article about that in the Jan issue of RCM.