Well actually, what I've used for the front half of my Python FTB nacelle is a Sea Fury cowling, with the rear end coming from a Swift (or was that an Attacker --- ). I measured and scaled a drawing of it, plus checked some dimension from the Wyvern kit so I could arrive at what I've built so far. So Greg's profile in the first post of a Hornet with Centaurus engines might work. However in the RW, the Python is as Jon says, enormous, it would take in the whole of the nacelle that I've made for my model, whereas the Merlin in the next nacelle over, the end of the engine is before the wing leading edge.