KiwiBiggles
Senior Airman
Well the choices might open up if Bristol avoids the love affair with sleeve valves with (crudely speaking) a double row Mercury and a double row Pegasus. Thus a 1,700bhp and a 2,200bhp radial. Double rowing 4 valve headed motor can't be worse than developing sleeve valves.
I understand that the reason Roy Fedden persisted with sleeve valves was that he couldn't find a way to make a two-row radial with four valves. I can't remember the source for this, but I would note that all the poppet-valve two-row radials had only two valves.