To accurately treat chemical reactions, methods based on quantum dynamics may be required. For most reactions involving several atoms, applying full quantum dynamics is presently prohibitive in terms of computer demand. One option is then to use reduced dimensionality approaches. Here we will focus on the Rotating Bond Umbrella (RBU) model and its application to atom-methane reactions. In the RBU model four internal motions are treated explicitly, viz. the breaking and forming bonds, the umbrella motion, and a reactant bend motion, which becomes a product CH3 rotation. Hyperspherical coordinates are used. Here we describe how accurate boundary conditions are applied and how the matrices relating to the angular degrees of freedom are diagonalized using the iterative Guided Spectral Transform eigenproblem solver. We end by showing some illustrations of calculations for the A (A=H,O,Cl)+CH4 → HA + CH3 reactions and a deuterated analogue.