Trouble is the 800 doesn't have a diesel engine at each end like the HST. The 5 car set has a diesel under the floor on coach 2, 3 and 4 whereas the 9 car has them under 2, 3, 5, 7 and 8 as far as I am aware. So you will need more that two decoders. Also the train is powered by overhead electricity and the diesels are for emergencies or where there is no overhead.