If anyone's interested in a 3D-printed Stirling Class F or an upgraded F1 version then there's a development discussion going on over at the 'other' forum:
http://www.rmweb.co.uk/community/index.php?/topic/134891-turbosnails-workbench-3d-printing-rtr-detailing-and-general-bodging-secr-f-class/ (http://www.rmweb.co.uk/community/index.php?/topic/134891-turbosnails-workbench-3d-printing-rtr-detailing-and-general-bodging-secr-f-class/)
Some scratchbuilding will be involved, but it would be nice to get more support for the N gauge version. The initial development is for an OO type, but the builder has already made it clear that he's quite happy to produce this in N too and it seems that a prototype N version is already being worked on.