Bounded-region conjecture for Whitehead-graph feature vectors

Let $F$ be the free group under consideration. Associate to each element of $F$ the feature vector of weights of its Whitehead graph, viewed in the corresponding feature-vector space. Partition these feature vectors into classes according to the regions described below, and call a class Nielsen-reducible when all its elements can be reduced by the same Nielsen automorphism.

Bounded-region conjecture. The feature vectors of weights of the Whitehead graphs of elements from $F$ are separated into bounded regions in the corresponding space. Each such region can be bounded by a hypersurface and corresponds to a particular Nielsen automorphism, in the sense that all elements in the corresponding class can be reduced by that automorphism.

The claim is presented as one of the conjectures arising from empirical evidence about selecting Whitehead automorphisms efficiently. The supplied text does not define the feature-vector space or provide evidence that the conjecture has been resolved.