All gas engines with diaphragm carb's can do this, not just DA. The pressure in the cowling affects the vent side of the diaphragm, changing the mixture. Getting that vent to be at a constant pressure is the goal. I don't know personally which one of these methods works best. The fuse can change pressures just like the colwing so that's not a guranteed solution. I like the balsa box but if that's in the cowling or fuse couldn't it still change pressures albeit a little more dampened? The fix that 3W uses makes the most sense to me. Since the carb's vacuum that pulls on the other side of that diaphragm draws air from the venturi outlet, it would make sense that you want the diaphragms vent side to sense that venturi inlet air pressure. That way the carb is pulling air and fuel from the same reference pressure (venturi inlet/carb air inlet).