Stirling Single, GWRdriver
Regading your coments on cylinder castings for the stirling single in 31/2 gauge. I have built the Clarkson version of sterling and Conway. Having just had a look, the conway castings are considerably longer. This is bad news because the pony truck splashers on the sterling interfere with front of the cylinder with the shorter correct castings. On my loco anyway.
Sorry to be the bearer of bad news.