  We present a detailed description of N=2 stationary BPS multicenter black
hole solutions for quadratic prepotentials with an arbitrary number of centers
and scalar fields making a systematic use of the algebraic properties of the
matrix of second derivatives of the prepotential, $\mathcal{S}$, which in this
case is a scalar-independent matrix. In particular we obtain bounds on the
physical parameter of the multicenter solution such as horizon areas and ADM
mass. We discuss the possibility and convenience of setting up a basis of the
symplectic vector space built from charge eigenvectors of the $\ssigma$, the
set of vectors $(\Ppm q_a)$ with $\Ppm$ $\ssigma$-eigenspace proyectors.
  The anti-involution matrix $\mathcal{S}$ can be understood as a Freudenthal
duality $\tilde{x}=\ssigma x$. We show that this duality can be generalized to
"Freudenthal transformations" $$x\to \lambda\exp(\theta \ssigma) x= a
x+b\tilde{x}$$ under which the horizon area, ADM mass and intercenter distances
scale up leaving constant the fix point scalars. In the special case
$\lambda=1$, "$\ssigma$-rotations", the transformations leave invariant the
solution. The standard Freudental duality can be written as
  $\tilde x= \exp(\pi/2 \ssigma) x .$ We argue that these generalized
transformations leave also invariant the general stringy extremal quartic form
$\Delta_4$, $\Delta_4(x)= \Delta_4(\cos\theta x+\sin\theta\tilde{x})$.
