What's the point of the Total In-Flight Simulator?
There's a detailed and very interesting Air Force paper on this: CAPABILITY OF THE TOTAL IN-FLIGHT SIMULATOR (TIFS). The main point it makes is that TIFS wasn't just about gathering aerodynamic data, it was about testing aircraft configurations (including cockpit layouts) in actual flight, and training pilots on them. Here are some extracts, but you can read the paper yourself for the full details.

Test different configurations:


  It also surpasses the utility of past variable stability aircraft
  through the realism possible in its separate, new evaluation cockpit.
  The capabilities and features of this in-flight simulator considerably
  broaden the ability of the aircraft designer to deal with difficult
  trade-offs in flying qualities problems. A base configuration can be
  set up and then its stability and control characteristics can be
  systematically varied for investigations to gain research knowledge
  pertinent to flight vehicle and flight control system design.


Simulate a number of very different aircraft:


  It has been designed to reproduce in actual flight the flying
  qualities of a wide range of large airplanes.


Test different cockpit configurations:


  The simulation cockpit is removable, so that it can be replaced by
  other cockpits of different configurations.


Simulate a new design in flight, before the new design has even been built:


  Flight evaluations of the flying qualities of new airplane
  configurations can be accomplished, such as investigation of the
  behavior of extremely large airplanes. This can be extended to
  investigating the flight control characteristics of entirely new types
  of designs, as for example, reproducing the landing approach flight
  characteristics of a large re-entry vehicle.
  [...]
  The flight characteristics of specific aircraft can be simulated in
  great detail, both to evaluate flying qualities in advance of the
  first flight of the actual airplane and to investigate difficulties
  that may arise during the airplane's flight test program.


Train pilots on new aircraft:


  Finally, a well established and highly valuable use of in-flight
  simulation is pilot training. In-flight simulation of emergency
  conditions can be conducted safely because, if the evaluation pilot is
  having control problems, the safety pilot can switch the system off
  and resume control of the normal base airplane