True, but we don't `see' that angle as easily as we `see' the airspeed of the model, and as the weight of our model is (usually) fixed, then the airspeed at which this angle is reached is also the same every time, so you can say that it stalls at an airspeed, and for our purposes it is sufficient. The plain flaps mentioned at the beginning are likely to make the model pitch up, will make the model slow down a bit (extra drag), and may reduce the stall speed `a bit'. That is assuming a moderate amount (45 deg.) of droop. More will produce more drag, but probably not much `more lift', less just less of everything up to some `best angle'. Much experimentation will be required.
Evan.