Inaccurate performance data for BOB fighters in COD comparing to RL data

[Crumpp]

In the Merlin engine, it is my understanding that, the spigots were on the cylinder liners. The Cylinder Head had recesses that accepted the spigots (presumable to ensure accurate alignment).

I don't think any other spigots (if any) on the cylinder head have anything to do with the modification.

You are very close. There are lots of spigots on an engine. They can be plugs, cylinders, etc...

You are also right in the cylinder liners form the spigot on many engines.