Sounds like you are looking to add stiffness to a marginal span. Unless you have the structural engineering expertise to calculate the effects of such non-standard constructs, I'd say avoid them. There is an excellent article in the current issue of Journal of Light Construction about "bouncy" floor systems and how to avoid them. The thing I found interesting is that floors with a natural (i.e. resonant) frequency of 8-10 Hz were judged to bouncy. This, they point out, happens to be the resonant frequency of our intrenal organs. At about 15 Hz floors were judged acceptable. They suggest upsizing from the normal L/360 deflection to L/480 for floors not supported by a girder. It gets more complicated of there is a girder.