I've always thought Park Avenues and Le Sabres were almost the same car (too lazy to look up chassis name), and the PArk Ave can ride 22's stock, so I'd imagine the Le SAbre can.
If you DO cut into the fender well, make sure that if you're taking off chunks of unibody you weld up tubes for braces braces.
A guy with an Olds Alero on 22's (and bags) had to hack into his unibody really bad and he didn't brace it. Go figure, now the car is twisted slightly. However, another guy with an Alero on 20's cut into his unibody to bag it and drop to the floor was ok because he braced the hell out of it. Just rmeember man, structural ingetrity ain't worth ridin' high.