Regarding this quote that has popped up in this thread:
"To increase the performance of the Me 109 an increase in the revs for a short time at heights over 5.5 km. will be in future be
permissible. For the DB 601 A engine the normal maximum revs are 2400.
Above full pressure height they may be for a short time be increased
from 2400 to 2600."
Here is the source document for this quote. It would appear to be a translation of a captured German document. It would also appear to be conditional on Auto Prop pitch installation. Sorry about the quality its as good as I can get. It does put into perspective the use of this increase in RPM and the issues associated with it.