yes the bracket the sliders attached to is screwed into the frame but the actual slider itself, which will be taking the brunt of weight, does not have the support of the frame to take the impact. That bracket will bend under the weight of the bike and the back of the slider will go into whatever part of the engine its covering. With all the pressure being focused onto one of those it might as well be a spike. If you have a no cut slider where the back of the slider is only going to impact the frame in a crash or tip over then the engine will be fine but of the several brands of no cuts ive seen, none of them are like that.

 

Oh, ok, thanks nick, I see what you're talking about.