I agree that the sliders will prevent damage, but if the scrubbing is as bad on 285s as I've read, it seems like they could cause some pretty serious damage off road without spacers.
Being cautious of turning is ok on the street but there are times off road where the ruts are gonna point your tires the direction they want them regardless of how carefull you're trying to be (and more violently/quickly than you'd turn in any normal driving).
Also I'm not sure how strong those rocky road super sliders are without the reinforcing from the body (since the slider to body mounts were cut off). They only have two small legs running to the frame because of the extra reinforcement they were designed with (that has been cut off on that set). Most other brands use at least 3 legs (larger legs). I think the trail gear sliders would be stronger than that particular set.