I fly La7 sometimes, heres a couple of tips:
1) Think of the La7 as a rocket with cannons.
2) La7 is great vertical but I think sucks flat turning. Don't flat turn with anything that turns well (N1K, Spit, Zero, Yak, P38, some 109's etc). In fact I just don't more then half turn at all.
3) La7 loses its best attribute (speed) above 7k or 8k, up there 190D9 and some other birds have speed advantage.
Tactics I've found good
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Find a furball somewhere, get some alt before you arrive, dive down to about 500mph, zoom through on Wep, kill anything that gets in the way, get alt, repeat.
I got 15 kills doing this the other day b4 my brain died and I HO'ed a mossie