ORIGINAL: Oryx
To get back to whether any of this applies to models: On models we can tolerate a slight negative static margin since the low inertia of models (especially your light foamies) keep the time-to-double of even a slightly unstable model within flyable limits.
...snipage...
Full-scale and models can mimic each other's capabilities under certain circumstances, but there will always be differences due to the differences in inertia, aerodynamics, etc at the different scales. What stays the same, though, is that they all operate under the same laws of physics. That is why engineers and scientists don't spend much time during their training on the detail of how a certain airplane/bird/insect flies (except when examples are needed to understand certain concepts), but rather on the fundamental physics. Once you know the basic physics and how and why things scale in certain ways, applying it all to anything from a bumblebee to a B-52 becomes fairly straightforward.
The first part of what I quoted from Oryx is an excellent explanation of why Dick's "CG can go anywhere" position works for light models. The CG governs static stability, but the dynamics (inertia and damping) are so benign that a human pilot can respond to and control the airplane. Light weight and a large tail are where it's at. The difference being that on the SU-30 the dynamics require a flight computer to respond quick enough -high wieght and slick airframe. But it is a good comparison by Dick, as it is essentially the same thing, with the object of both planes being maneverability due to low static stability. One twitches slow enough that a human can control, one uses 'power steering'.
Most people do not have a grasp of dynamic stability/dynamic response and cannot see further than the CG position in relation to stability. This is why the second half of the quote is so important. I have never seen physics/aerodynamics fail to explain any flying object. When I see someone claim this, it is doubtless someone who knows "just enough to be dangerous" without knowing how to apply all the rules.