Spit Mk1 Boost?

[Crumpp]

Sea Hurricane IC used 16lb boost in combat, but not in 1940.

Only after significant modification to handle such pressure, modifications that did not exist in 1940. Your document clearly separates it from the earlier Merlin II and III engines.

The +17PSI is not mentioned in any Spitfire book, this is simply a figure the Merlin III achieved (not safely mind you!)

It has no bearing or relevance. BMW tested the BMW801D2, including flight test of the aircraft, to 2.2 ata but the engine never saw a service rating above 1.65ata.

It is not intellectually honest to make the claim the engine was then capable of 2.2 ata. It was not capable of reliable operation at that boost level and that is reason it did not enter service. Same goes for the Merlin II and III.

If you want to know what an airplane can do, check the latest edition of the Operating Instructions. That is what was approved and in use.

No speculation required!!