I'd be interested to know what thrust setting they need to maintain a zero acceleration during the arcs in the 727.
I've pondered this just a bit, and since they want zero longitudinal acceleration (as well as other axes) then a thrust just equalling drag is the correct answer.
Given that as altitude increases, speed bleeds off, then thrust must decrease too as does drag. Similarly, after rounding over the top, as airspeed increases, so must thrust.
But lower air density over the top means that thrust is dropping without any throttle movement. Whether the density falloff coincides with the speed/drag/thrust requirement I'm not sure, but as a first approximation I'd say little throttle motion is needed.
Further enlightenment welcome!