Spit Mk1 Boost?

[IvanK]

12lbs Boost was available to both the Merlin III and the Merlin XII (running 100 Octane) when Boostcutout was activated. In the case of the Merlin III a couple of mods were also required to allow 12Lbs Boost. This has been debated at length in the forum.

Only the Merlin XII had the +9lbs limit Full throttle. (Boostcutout not activated)
The Merlin III Limit was +6.25Lbs Boost. 9Boostcutout not activated)

I don't have links to the docs. I spent a bunch of time in the UK archives researching and copying them. Pretty much every RAE report is available there.
Bits and pieces of these docs are available online at Spitfire Performance testing and WWII Aircraft performance http://www.wwiiaircraftperformance.org/