I would suggest you only go as big as you actually need with injectors. If you only need 500cc.. then just get 500cc. The only positive with running anything larger is they will cope with more demand down the track, everything else is a negative, poor economy, poor idle, etc.. under light engine load (which is going to be the majority of the operating conditions), it will be a bit like the ECU trying to measure out exactly 5.25ml of fuel using only a 10L bucket..