Light models fly slower than equivalent heavier models; hence, the first ones require less energy to sustain flight than the second ones.
In consequence, a stall – spin should be stronger and more dramatic for the heavier ones.
In some extreme cases, the little forces and speeds involved in the ultra-light flight are insufficient, just by deflection of the elevator, to force the wing even close to the critical AOA.

Unfortunately, not all models can be built that light.
Scale models are a good example.
Models designed to fly in strong winds are another example.

Those are the models that are affected by this type of stall.
Some of the pilots of those relatively heavy models will beneficiate from the discussions of this thread, I hope.

Here are two examples of stall – spin for full scale airplanes:

http://www.youtube.com/watch?v=08D9qDyFG8s

http://www.youtube.com/watch?v=b_cgzbq3vUQ

Scary, isn’t it?

Note that the stall in turns is non-symmetrical.
One half-wing reaches the critical AOA first and the stall begins ONLY for that half.
The stalled condition makes the drag increase rapidly for that half-wing, which slows down and produces minimum lift.

The airplane yaws and rolls around the CG, while noses down pushed by the pitch moment that the stalled half-wing produces.
In the meanwhile, the other half-wing continues flying faster and lifting.

This way, the spin that follows the non-symmetrical stall feeds itself.
The plane falls in a spin which center is close to the tip of the stalled wing, while the non-stalled wing keeps flying fast around that center.

The way out of this condition is to break the arrangement of forces acting over the model in a non-symmetrical way, while the stalled half-wing recovers normal air speed.