Cheers guys!
Re-thought my strategy re fuselage construction. It will be better to join the modified nose sections to the rear fuselage halves before scratchbuilding the cockpit, as the visible area extends beyond my cut off point. Want that join to be nice and smooth before detailing.
Closer inspection of engine photos shows the thinner section of the cylinders shouldn't be visible beyond the outer rim of the streamlined reduction gear housing. Turns out the RPM/Pantera, Mastercraft, and Siedlce housings are all too narrow in diameter, RPM kit item by 1 mm. This may not sound much, but is very noticable in 1:72.
Will either modify a spare spinner of correct diameter or modify the Mastercraft P.7a engine (which does actually have the nicest cooling fin detail)