Indeed, chaps. One of the things that I also noticed was that heating & cooling i.e. cylinder condensation and re-evaporation is the major efficiency problem in simple engines, hence compounding - each cylinder now works within a narrower temperature band, so less energy is wasted on the heating & cooling.

Oh, and one way round the "bigger cylinder" problem is split your Low Pressure cylinder. There were a number of triple designs with 4 cylinders i.e. two LPC's (doubles with 3 as well). In fact, large liners such as the Olympics often favoured them, because if you stick one half of your LPC at one end & the other at the other, you get a better balanced engine & a lot less vibration. Got to look after the passengers...

And another random fact - what did for the reciprocating engine was the steam turbine, of course. HMS Dreadnought, which broke the mould in so many ways & became a generic word for modern battleships, was the first major warship to be powered by turbines, rather than triples. She was still coal-fired, mind you!