Red Wine, I'm a little confused by your stating the manu. to make their planes unstable by aft c/g. All a/c are flt tested to an acceptable c/g range. The more forward the a/c is loaded the more stable it is. Futher back in the c/g range decreases stability but increases fuel economy.
The MD-11 works like this, after t/o and clean the fuel system controller starts to transfer fuel to the tail tank to control to an aft c/g to reduce the need for nose up stab which is a source of drag, doing this nose up input by weight of fuel instead. Of course, all this time the auto-trim is taking out all steady state elevator loads. Don't kid yourself, an aft c/g can ruin your day in a hurry, especially if combined with an altitude selection above optimum. Do a search on MD-11 high alt upsets of which there are many, all caused by aft c/g, above opt, with turb.