Mention is made in a couple of books of the plan to combine Caprotti valve gear and the preheater Crosti boiler in variants of the Standard Class 5. In the event, these were never built partly because the 9F Crostis were hardly an unqualified success. In fact, not a success at all...... It was therefore felt that the potential efficiencies from the boiler and valve gear combination would never arise in practice.   So here we go.....   I've come across 2 drawings of this: one in the Edw