In the Hangar:
Set your wing gun convergence to 250. Set your nose gun (cannons) convergence to 350. This will give you a chance to hit with your cannons out to around 700, which is about as far as a cannon shell will fly. You'll see some drop-off around 500 so only do the long-range shots if you're shooting at a very large target, like a bomber formation.
On the runway:
WEP on autolaunch up to 8k, or until the engine temp needle is 2/3 thru the yellow part. Then, just normal throttle on autoclimb up until the needle is below the yellow part of the temp gauge and WEP it on up some more. DON'T let it go all the way to red because it'll take too long to cool back down and you never know when you may be needing to use that WEP in a dogfight.
In the air:
Set your views while you're on autoclimb. I like to scroll my views all the way back, and in the BACK/LEFT and BACK/RIGHT I like to scroll it back so that the radio mast and rudder are on the edge of one side of the screen for maximum coverage. Same with UP/BACK/RIGHT and UP/BACK/LEFT. For the forward views, I raise my FRONT view so that the gunsight is just a hair higher than normal and scroll back so that I get a good field of vision but can see all of the guages, too. I scroll my FRONT/UP view all the way back. In a dogfight, this will be the view you'll use the most often so you'll want to cover as much space as you can.
In combat:
The best range to shoot the Ki-61's guns is anywhere inside of d300, preferably around 250. The Ki will run through its load of cannon quickly, so think like a sniper - short shots, brief burst, quick kills. If you're trying a low-percentage shot, just use your wing machine guns. I've actually downed aircraft with just a brief burst of the machine guns alone. Maybe I got a lucky cockpit shot or maybe they were already peppered by somebody else, but I got the kill so it works.
The maximum effective ceiling for the Ki-61 is right around 20k. Any higher and you risk a stall doing simple maneuvers. At that altitude, you'll want to avoid engaging higher bandits, and in a special event it seems everybody tries to climb to max alt.
If you find yourself under an enemy swarm, go into a shallow dive to build your speed and sucker them down. If they suck, they'll keep their throttles open and you can either turn with them or outturn them (depending on what you're going up against) and force them to overshoot your turn. As they fly past you, just correct your flight path and give'em a quick squirt of the guns (and only a quick squirt - it doesn't take much from the Ki's cannons to down a plane). If they're good, they'll chop throttle and turn it into a turnfight, in which case you should chop throttle and turn with them (all of the IJ planes turn well enough). Once you see that the enemy is getting an advantage on you, go nose down and dive away. The Ki accellerates well in a dive and you should be able to either (a) escape cleanly or (b) force them to dive, too, in which case you turn it into a high-speed turnfight by going fast, then looping up (use WEP to help keep your speed up here - that's why you never let your engine temp get too far into the yellow) and try to lose them when they black out.
A lower enemy is a dead enemy. If the enemy is in a plane that turns well, like a Spit V, or FM2, don't follow him down if he does a split S. What will happen is that you'll accellerate faster than him and overshoot, in which case he'll correct his turn and do to you what I told you to do to him: force the overshoot and give'em a quick squirt as he goes past.
If the enemy is in a plane that doesn't turn as well as the Ki - such as a P-51B or F4U birdcage Corsair - then you can follow him down and chase him around a bit. One thing you shouldn't do is become fixated on the target. Get in the habit of looking behind you if you're chasing an enemy for awhile. Chances are there's another P-51B or F4U chasing you, too. If you look back and see something back there that's red, DON'T pull straight up! .50 cals have a long trajectory and the Ki has a weak structure. Instead, do a quick 45-degree roll and then pull up so that you're on the edge of a black-out (this (a) preserves your pilot's consciousness and (b) is a good way to avoid losing too much energy).
During all that turning, keep testing your "drop flaps" key. If you hear the flaps deploy, then you know you're down to around 200ias and should make sure you've got enough air under your feet to dive away if things go bad.
If you get into a low-speed mid-alt turnfight, feel free to keep those flaps down to improve your turning and get in front of the enemy plane's turn flightpath. Avoid getting below 10k unless you're chasing a baddie or strafing a town.
If you get caught on the deck at low speed, fly like a 109E - lots of flaps and WEP to keep your engine pulling the load in the turns.
