This paper addresses some open problems in the area of dynamic output feedback control design. The first one is the structurally constrained decentralized control problem, and the second is related to robust and reliable control. A necessary and sufficient condition for decentralized and quadratic stabilizability is given and used to provide a solution to the H-2-norm optimization problem. A numerical cross decomposition algorithm is developed and satisfactorily applied to find the solution of some illustrative examples. A comprehensive benchmark validates the results.