As I said when I visited, it's a shame it's so small. I'd really like one a little bigger, gauge 1 (1:32) on bespoke gauge (18 mm) track sort of thing as the next size up readily available is the G scale Accucraft version.
Whilst the SAR interest bubble was circulating and just for giggles I drew up some upgraded NGG16 to fictitious heavier variants for hillier grades.
The NGG18 is a 2-8-2 + 2-8-2 design with enlarged boiler for the extra capacity and modified sun glare cab as seen on many Cape gauge Henschel locos.
The NGG18A is a second later batch with more modern rounded tanks and Giesel ejector.
The NGG20 is reduced axle loading variant on a 4-8-2 + 2-8-4 configuration, the rear tank originally being coal fired with automatic stoker (hence the raised profile to house the stoker screw), since removed and converted to oil. Also fitted with modern high beam head lights.
In an ideal world you'd use much of the Backwoods model for the castings and various other parts, then etch or scratch the bits in between, idle minds are terrible you know