May I chime in here and ask a (hopefully) unambiguous question to clarify this, as I am interested in the answer also.
A) Company pays for a 27k bump engine with 22k 24k 26k derates.
1. Takeoff at fixed derate 22K. Firewall, what do you get?
2. Takeoff at 24K assumed temp. Firewall, what do you get?
B) Company pays for a 24K engine. Takeoff at 22k assumed temp. Firewall, what do you get?
I could try it in the sim soon, but perhaps someone has the horse's ear on this.