Vudak, Thanks.
The K-4 climbs like a ground-raped monkey - indeed is probably the best vertical fighter in the planeset. I say that as a guy who also likes the Tempest and all the F-Dubs. Generally, if I need to reverse in a K-4, I'll pull vertical and loop and roll - an Immelmann, I guess. Thus, I should be able to always stay above a non-perked F4U and get on his 6 via an Immelmann, correct?
From there, I should be able to get a firing pass - there's probably a solution for single shot, maybe two with the tater gun before he evades.
The good news, if I read you right, is that he shouldn't be able to touch me as long as I start with an altitude advantage - although he'll always have a better low-speed flat turn and I'll always be watching my airspeed on the downside of those verticals.
Probably the next F4U I see will be a HO. But, doubtless, this'll come in handy someday. I always try to remember, e.g., with the D-9 (stay fast, don't try to turn fight with a Spit, Yak, A6M, etc, don't try to outdive a P-47, don't ho with an IL2... etc. etc.) what my advantages/disadvantages are but really hadn't analyzed the F4U yet.
There's no trick that works every time, but let's say you were diving in on his 6 and he made a hard break turn to the left. If you follow him, try to pull lead pursuit to shoot him in that break turn, he is going to use your speed against you, barrel roll to the right, and put you in front of his guns.
Instead, you have a few options. When he breaks, you could pull back on your stick to start a climb. You could then roll to your left a bit to keep him in sight, and begin pulling towards him from higher above, and still in his six. If he reverses towards the right, you could then do the same thing, but this time to the right. Remember, every time he makes a hard, flat, break turn, he is losing energy. When you go up, you are banking a little. Once he makes a few of these, he might still have the energy to be able to turn a very tight circle, but will he be able to get around it before you swoop in for the shot? That is the question.
Alternately, if you have an incredible excess of speed, and he breaks hard to the left, you could go up, and make a large barrel roll towards the right. When you are coming towards the bottom of your roll, you would then pull towards him. This is assuming (for simplicity's sake) that he elected to just go for one 90 degree break turn.
The idea I'm trying to get across (and hopefully someone better at expressing it will come along shortly) is that in a general, over simplified sense, if you're faster and on the Corsair's six, you have three pursuit options:
Lead, Pure, and Lag Pursuit.
Lead will see you pulling for the shot in his break turn, possibly missing the shot, and quite possibly overshooting him;
Pure pursuit will cause your bullets to miss (in this example, since he's breaking and you therefore need to shoot ahead of him), and will also allow him to reverse you, causing an overshoot;
Lag pursuit will help you stay behind him, to set up a shot later. The two ideas listed above are examples of how to try and stay in lag pursuit.
I wouldn't go with an Immelman, as that would have you going in the opposite direction, and at the start of his break turn we do not know if he is going to extend it a full 180 degrees. If he doesn't, and you do, now he's bought some time to build up some energy, and you have to waste some to turn back towards him and eventually dive down to get him.
Edit - at some point you may want to dump some speed to pull for a shot... It is a balancing act of being able to put guns on your target, not overshoot, and still have the E to follow his next move. Practice, practice, practice 
Hope this helps
