It is possible to half size the Idris loco ( O gauge) I am currently building 3 O gauge Idris (Dave Watkins plans - free download, not sure of the address). I have a penchant for half sizing a lot of the plans I get hold of. Ho live steam is very successful, and has been done ie Heischler, Hornby live steam (I have 2 of them). N scale and Z scale have also been done in the 70's. Good thing about making them smaller is you only need small machine tools.
