stretching tire works for certain tires (not shitty ones). it actually puts the whole contact patch on the ground (assuming you have correct alignment settings), and it usually stiffens the sidewall. it's used in grip type setups, and in drift setups, as it gives a very smooth and linear breakaway in the rear, as there is less tire bulge and sidewall flex to allow the tire to maintain grip. up front it's not as necessary to stretch, but i havnt read up enough to know the front benefits.

alot of it is aesthetically pleasing, fitting a wide rim with a really low or negative offset under a fender with a stretched tire, cambered in to make it "flush". but if it's just for looks and the alignment sucks, then its no good, function > form.

and stock 240sx rear camber is somewhere around -1.5 degrees if i remember right due to the stock rear arms, and "sporty" feeling the designers went for (eccentric bolts are designed to adjust it close, but suck balls). running negative camber obviously causes the point where the load on the tire is to shift inwards (going negatively in camber terms), causing premature wear. most people slam their cars (myself included for now), and stuff expensive tires in the back, then bitch when they wear them out fast on the insides (and most unidirectional tires have to be unmounted, flipped, and remounted if u want to rotate them, unless u keep them on the same side up front which will offers no benefits, and most people stagger different sizes making it goofy looking to do the front to rear tire rotation). ruca's alone will cure the camber but if u want to run negative rear camber, it throws your toe spec out of alignment. getting toe back to zer0 or close is the way to run negative camber in the rear and still have good tire wear (it also depends on the driving style/compound of the tire/pressures used).