That diving spiral is more or less a move of last resort to keep them from drawing a bead in hopes you can gain enough separation to straighten out and motor away. Ideally you want get them out of phase and work it so that you extend in the OPPOSITE direction your opponent is facing. However this is a defensive move and you don't have many options to re-engage directly from it unless your opponent makes a really bad mistake such as an overshoot. Once you commit to this your best hope is to shake them off so you can withdraw and re-enter the fight from a better position. You can use a low-AoA high-speed climb once you have some room to straighten out (with gunnery in here, you want at LEAST 1000yds separation). You may not climb as high, but the F4U can hold on to airspeed for a LONG time like this, and really scoot away from slower opponents--even those who will out-climb you like the Spits. IF you have sufficient airspeed and separation.
Keep in mind that while this may work in a large fight where there are other targets your opponent needs to contend with (particularly those at co-alt or above) and can't devote himself to chasing you down, (granted if he DOES get fixated and you have a friendly nearby, you CAN use this to initiate a drag-and-bag....) in a 1v1 he can just pull out and pursue you from a perch which puts you in very little of a better position than when he was D800 on your Six and closing.
Another option is a situation I was in tonight:
The skies were completely clear in all directions, above and below, while I'm searching for a target near an enemy airfield. All the sudden I look back and have a 109G-14 about 800yds out and closing (no idea WHERE he came from, either. There wasn't so much as a dot in all directions for the time I was circling, with plenty of checks to the rear and rocking to clear my Low-6).
Priority 1: React to the immediate threat.
I snapped into a low-yo to the left, turning back into him to throw off his attack run. I was cruising level, so had a decent amount of speed (gotta love the 350mph cruise speed on the F4U) and couldn't get my flaps out. The G-14 attempted to turn with me. I was still in his front arc, but had prevented him from gaining a clear guns solution and spoiled the bounce.
Priority 2: Reverse the bastage.
The 109 was now within 400yds, but unable to pull lead. I continued through my low-yo (it ended up as almost an oblique Split-S) into a high one. The G-14 continued to follow, and we ended up in a looping fight. As we continued looping I continually made alterations to my bank angle. Sometimes I came more straight over the top, others I was in more of an oblique/high-yo. By now our airspeeds were dropping and as I was able to bring my flaps into play I started pulling around on him. The 109 did the smart thing: He broke off and grabbed out. Had he not, I was maybe a loop or two from being able to roll over into a guns solution and a victory. A G-14 WILL out-climb the 1-series Hogs (I was in my 1A) and I had no intention of trying to follow him up, so I unloaded my flaps and turned for home in a shallow climb, watching him all the way and waiting for him to try coming back in (he didn't and decided to pick on a friendly that arrived shortly after we separated instead).
Do NOT stay defensive. If you stay on the defensive, you're only delaying the inevitable. The only defensive maneuver you should make is that first one to avoid the initial attack. Once you clear his first pass the next thing on your mind should be, "How do I get on HIS Six from here?" It could be dragging him into a looping fight, or extending out in a shallow high-speed climb to neutralize his E and altitude advantage. Diving out with a spiral is purely defensive. That's not to say there's situations not to use it (I do myself if I'm in a really bad position and out of options) but it should definitely not be your first move as there's very few places you can go to reverse the situation.
...and I reversed using the F4U's ability to get slow...
Again, you do NOT want to use that capability against the Zeke. Stay. Fast.
Depending on the stick you MIGHT be able to pull it off against a Ki-84 as your flaps can come out well before his can and the Corsair has a very good instantaneous turn on that first notch, but you damn well better make that first shot count. Against 109s it really depends on the type. The E and F both turn too well so again, don't get slow if you can avoid it and stay fast. The G-series, especially the G-14, you can take a chance with. The K-4 is more often than not going to treat you like a Zero and use climb and speed to try to keep you away. Against most pilots if you drag him in close you can dice him up if he tries turning with you, but if you've got an Experten on your hands he's going to vertical you to death so be VERY careful trading off your airspeed against the K-4. Remember the 1-series Hogs don't recover E very easily if you give it up, so once you decide to get slow you're basically committed to it until the fight is over. This is why I prefer to keep her fast and high in large fights.
