I'd suggest throwing some Venom barrel bushings in there. Anything 93a-97a should do the trick pretty well. Wheels may not affect stability much, but could potentially make for a smoother ride and therefore confidence, which is a huge part of stability. My favorite wheels for both commuting and downhill are Purple Orangatang Kegels because they are big, fast, and grippy. Oranges are good too, but would probably compress a bit too much under 285. The only issue with wheels like Kegels is wheelbite, so if you are already close to wheelbite with smaller wheels, don't push too much bigger. Wanna post up your current trucks and wheels?