The good news is that the arrangement of the discharge nozzle and the associated piping as you describe it will have little affect on the pump performance, so the flat side of the increaser (expander) will be okay. However, if you are installing a larger pump, I would assume you are increasing the flow. In which case, I would be concerned about the velocity of the flow in the suction line. This should be double checked to ensure you will continue to have adequate NPSH available for pump operation.