When it comes to the size of a plane in the target-
The target measures 100ft x 100ft. Each ring is 10ft from the others, the center ring being 20ft across. The F4U has a 41ft wingspan- compare this to the targets rings in this screenshot-
The way I like to test convergences is like this-
Set convergence to what you want (300 yds, say) and then put the target that far out and fire. Then take a screen shot of it, and reset the target to get the holes out. Then set it at a different range to see the effect of firing at non-convergence ranges. Take more screen shots, etc. I trim my plane while on auto-pilot (level) to maintain a center hold on the target, and allow my plane to reach full speed before testing. Not doing that will show useful information, but isn't a reliable test for
convergence. It can show the effect higher AoA has due to lower speed, effect of firing while tilted, inverted, or under G-load, etc... It can show how important it is to set up a shot so that you're level, and at 1G, and show you how to compensate for when you're not
One obvious thing I noticed was 300yds seems to be as "optimum" as I can get with the F4U (or any wing-mounted 50s). Setting my convergence to 300, and firing while at 300 will yield more hits then setting it at 600, and firing at 600,
even if my aim is perfect in both instances. Effectively, I've found that setting it further than 300 hurts the effectiveness of the wing-mounted 50s more the further out I set it. I've found that same thing to be true with any of the wing-mounted planes that I've looked at. My general rule is to set my guns at the same range any time I'm in a plane with wing-mounted guns. My main concern isn't hitting my opponent- my concern is hitting him effectively and reliably/repeatably/predictably. I want to hurt him bad, and hurt him quick. It helps me live longer
A side benefit to 300 is that it's one of only a select few distances I can fire at, and
know what my actual distance to the target is. So I
know I'm firing
at convergence. The only other times
I can do that is at 100, 500, 700 and 900yds. I consider 500 and 700 too far for serious attempts (but I'll still fire to "steer" my target. How do I
know my yardage? Watch the distance counter.
D400 means the target is somewhere between 300 and 500yds. That's a pretty big range, and setting convergence at 400 will only allow me optimum hitting power in the middle of that- how do I know he's in the right spot?? I don't. I'm stuck with a guess.
The trick that works for me is to set convergence at a point where the D-counter changes. My target is in front of me, and I'm closing on him, preparing to shoot. The counter says D600, then D400. I wait. The counter switches to D200- now, at that moment, how far away is he??? He's 300yds out! How far is my convergence set? When is the best time to shoot?
In reality, I set my wing-mounted guns to 275, and try to do most of my shooting at that range. I set it there because of my reaction time between seeing the counter switch to D200 and actually firing (remember, I'm assuming I'm catching him). The 50's are like chainsaws at that range, with that convergence. And, through my testing, I've also found that setting it at 275 leaves me basically as effective at 600 yards as I would be at 600yds with a 600yd convergence. The difference is that at that range I have two groups spaced about 15ft apart, and a little low.
Anyhow, that's how I do it... YMMV.