Oh, and by the way, at their first Northern Edge in 2007, the F-22s attained a 144-0 kill record against multiple threat engagements (F-15s, F-16s,
and F/A-18s). This included many 4-on-1 scenarios, with the F-22 being the "1"
That DERA study is well over 10 years old - infact, it may be over 15 years old by now.
edit: (2 liner), and the 'study' was based on guesstimates of performance. How accurate those guesses were, we don't know.