I dont have the technical expertise to add much more but from experience the Yak U hits a brick wall at 200mph acceleration wise. The spit you were just trying to get angles on will out accelerate you, probably the N1K too, if you disengage at this speed and dont have the option to dive.
One other thing, if you manually set climb to just a shade under 2K a minute at low alt, and you have enough seperation from faster planes at equal levels of E - La7, 190D etc you can maintain that gap till more options become available.