The regioselective synthesis of easily isolable pure bismethano derivatives of C-60 and C-70 with high steric congestion is described using 1,3-dibenzoylpropane bis-p-toluenesulfonyl hydrazone as the addend precursor. When the addition occurs at two [6,6] ring junctions within the same hexagon, bisadducts with mirror symmetry are obtained for both C-60 and C-70. When the addition occurs at two [5,6] ring junctions in C-60, a symmetrical adduct is formed, which readily undergoes photo-oxygenation and ring opening to yield a fullerene with a hole in the cage. In this work, we also propose a simple and general system to name all of the possible [6,6] bisadduct isomers on C-70.