stilton:
On an individual basis, flex / reduced power take off's do not save fuel.
Whilst not the most cost efficient profile when taking into account all other factors a full power take off followed by a max continuous thrust climb to altitude will save the most fuel.
You have stated this quite correctly, given your condition of min fuel for max range. I believe this is true for most turbofan aircraft.
Just don't overlook the " taking into account all other factors " for more mundane ops. Those "all other factors" are far from trivial.