[en] The cost of structural components in a large superconducting coil may well exceed the coil and cryostat cost. As a result, the idea of constructing a system composed of two different coil types assembled in such a way that the sources balance and reduce the total structural requirement is oft proposed. A suitable geometry has never been found for the fundamental reason that there can be no force compensated solution. In this paper, the general problem is presented and an analysis of the energy stored and stresses produced in the structure are described in a fundamental way. Finally, the relation between structural mass M and stored energy E, M ≥/rho/E/σ/sub w/, that is valid for all magnetic systems is developed, where /rho/ is the density of the structure and σ/sub w/ is the working stress in the structure. 12 refs., 2 figs