Glad the tip helped
The k4 can "gain and loose" E at will. So don't be afraid to lay off the throttle for a few seconds or even way more time than that.
Usually what happens when it goes bad is you get fast with the nose down slightly, trying for snap shots below your nose. Then it takes much longer to get your nose back up for the verticle turn. In this time they catch you. It won't really matter how slow you are as long as you can get your nose up immediatly when you need to. A nose up, flaps wingover will easily make them miss and you then have time to work the next angle for a shot.
The only time to be careful about low throttle is in a high speed situation. If they get speed over you they can use it against you. But if you have gotten them to slow down some then you have the "power" to cut throttle, drop flaps and cut the angles to guns.
But you have it right. Lots of power at only 40 or 50%. Resist the urge to wep it and catch them. You will just get real fast real quick and they will get a jump on angles due to the better turn. Be patient. IF you are close they will want to shoot you which is what you want. If they bug out get your speed back as fast as possible. You will need it on the re merge.
Like you found out the K4 will handle, turn and even climb just fine at half throttle. In fact doing this a few sorties a night will really help you understand the energy difference between you and the bandit. It will also force you use more angles and think about verticle turn more. It makes you aware of loosing and gaining energy and therefor forces you to manage energy by using the verticle either up or down to keep a constant E state.