Bozon, the climb on the N is equal to the D40 when off-wep when at similar weight loadings. The main differences are the charts on the N include full fuel so folks always claim it's way worse. It's not. It's like comparing a P-51D with 100% fuel and 2 DTs to a P-51B that has 25% internally.... sure the charts will look different, but it's not a useful baseline to establish!
As for the convergence, if you think it's THAT bad, it's in your head. They aren't that much further out than on the other jugs. The plug/insert into each wing was only something on the order of 10 inches. The guns themselves are staggered over more distance than that!
In ANY plane if you're saddling up on a yak point blank when your guns are set to 300, you're not going to do crap. That's just a sad fact of jugs, ponies, and about 1/3 the planes in this game. Even in a standard jug you're only going to barely hit one of his wingtips.
And if you're monkeying your rudder about to get a 10-yard shot with guns set to 300, so that ONE of your wings' guns hits the fuselage or cockpit, while wasting all your E and half your ammo, you're just doing it wrong.