I used to be prejudiced against them, but I have been flying them lately in disadvantaged base defense -- where they excell. Most people who hate the La7 hate it because of how many weak pilots use it as a HO/Rocket run/reverse and repeat machine. But, it's actually more fun (and more successful) if you fight it like you would anything else, with style tweaks to take advantage of its strong points.
I'm no ace, but here's my take:
* As with any plane, you have to UNDERSTAND what it's good at and what it's not, and how hard to push it. Think of it as a whopping big engine with wings strapped on...it's fast, it accelerates, it climbs well. In a fight, use what it does well and what your opponent doesnt!
* If you're in a crowd, keep it fast. If you slow down to get a kill, either have only a few enemiies around -- or be prepared to die. That doesnt mean you have to extend 10K before reversing; just don't give away lots of energy (alt+speed squared) and get down into, say, the Zero's favorite flight envelope. Now, it's quite possible to stall fight well in the La7, but MA stall fighters don't often get home, and that's what you're saying you want to do.
* Save your shots for up close. There aren't that many rounds, they fire slowly, and they scatter at longer ranges. Take shots you can make, and make the shots you take. (This is a must if you want to get long runs of kills in any plane!)
*If you turn, make sure you use the vertical. Your plane has lots of acceleration and climb; if you keep your nose generally up your opponents generally won't be able to keep up with the climb, and you'll gain position.
*On the other hand, if you get too sloooowwww in your climb you may allow a true stall fighter to drop flaps, briefly pull nose way up to get the angle, and recover from a stall while your wing flutters to the ground without you. Faster and wider favors you more.
*As in any plane, you need to get good at multi-con management. Good SA is a must, and you need to be able to judge who is the greatest threat at any given time. In fact, if you want to get a string of kills you need to stop thinking about SA as "remembering to look behind now and then." Situational Awareness includes everything around you -- where the enemies are, how close is the enemy base (where new, still unseen enemies will come from), how fast/high are the cons around you, which friendlies seem to be engaging which enemy and how likely are they to succeed, which 3K cons have a chance at a good shooting angle when they get closer.....you get the idea.
If you haven't tried it, I strongly suggest you drop in for a few of Widewings multi-con management furballs. They're in the TA, and are on the trainers' schedule. You take turns trying to survive one against 4-5, and you learn to when and how to convert to the offense to whittle down the odds.
You'll notice that a lot of "how to succeed in Plane X" comes down to general pilot combat skills. No plane has a formula; to succeed you need to understand how fighting works.