After a couple of months in store, and inspired by my visit to Narrow Gauge North, I revisited the loco and made several changes. The most significant was the use of a Sidelines (Steve Bennett) chassis frame intended to take a Tenshodo 24mm 'Spud' or a Kato Tram Chassis in 9mm gauge. This gives me an O-16.5/O9 option for the loco. As the sideframes for the chassis were intended for Gn15 I replaced them with some home brewed ones, incorporating Steve's castings for axleboxes from the Black Dog Mining O&K kit.
Various other examples of Steve's castings have been used, including the headlight and bell, coupler pockets, and a gearbox and handbrake wheel inside the cab.
It's certainly a bit on the big side for a 15" gauge loco, but certainly passes for 18" gauge in it's O9 form (which it is at the moment). Plans are in hand to develop something for it to run on (I hesitate to say "layout"), but that will have to wait for some time to come to fruition. I did however manage to put together a pair of wagons for it to pull, these run on Black Dog 5' chassis frames.
As I can't actually access my workbench at the moment (would you believe it if I said it had 20 square metres of tiles piled up around it?), the next update will hopefully look at some of the new loco's older siblings from the workshop....