Tailspin:
I am checking my Crowood "AIRCO The Aircraft Manufacturing Company" book and it says that the Max Speed for the Puma (230hp) was 120 mph, the Eagle I-IV (255hp) was 117 mph, and Eagle VIII (375hp) was 126 mph.
Sound like the easiest way to fix the DH4_data.ini is up the speed to at least 115 mph (using Peter01 & TW's formula of -5 mph off top speed per plane due to "wear & tear"). I can post a DH4_data.ini fix tonight after I test fly it to make sure the numbers match up.
As for the different engines, it said that the Eagle III (250hp) engines were replaced by Eagle VII (275hp) starting in Winter 1917-18 at unit level and Eagle VIII (375hp) were installed in late war DH4's.
Panama Red