For my cameo challenge layout I need to put together two sets of 8 CDAs, I have a box of the early 2000s Hornby models which will be the starting point.   At the moment my thoughts are to tackle 3 main areas: The chassis: First of all is the removal of the fictional box which runs along the length of the wagon, then I somehow need to get them fitted with P4 wheels (with break disks on opposite axles).  Not that easy given the limited space, though having seen a video on youtube of Hornby HAA