The AH Wiki doesn't say ANYTHING about flat turning.
Instantaneous turn is superb at all speeds and she's one of the best at high-speed sustained turns, especially when utilizing energy saving or building maneuvers such as the low yo-yo.
There's no such thing as "turn as hard as I could without bleeding the speed." A flat break is one of the WORST maneuvers for maintaining E no matter how you slice it. As boomer indicates, high-speed sustained flat turns don't remain high speed for long, usually not more than one or two circles at most before you've bled off all that E.
Against Zeros you MUST use the vertical: Either going up where you can use your superior roll and rudder authority to drop on him, or in a descending spiral/low-yo where you can accelerate through the turn, particularly to gain more E for the vertical maneuver (in short: low-yo closes but puts you in a lag pursuit, a high-yo will allow you to gain lead and a shooting solution).
Against Spits and 109s, if he's already in gun range on your six you've really screwed up. The F4U can extend on most IF you can stay alive long enough, but your level acceleration isn't nearly as good. Otherwise you should be able to run on all of them except the K4 and Spit XIV. The 109s you can really throw off by rolling to the right as they strongly resist a roll in that direction at high power settings.
As far as the HO, if a Zeke wants to HO me? Well, he can come and get it.