Further to my last post I've fitted my ex-Percy chassis with crossheads/piston rods and slidebars, and put the cut down Smallbrook studio cylinders at a raked angle, as per

He is quite right; 14BA nuts and bolts are seriously fiddly, but with a bit of care and thought about how to hold each bit, it's not all that difficult.

 

Here it is running:

 

https://www.youtube.com/watch?v=KG_Fv97OBPI&feature=youtu.be