I don't particularly like that design, since it is more of a hybrid body/frame mount. The problem with that type of design, is you are tying the sliders to both items, but they are designed to move individually. Not saying it wouldn't work ok with some rubber bushings, but it appears to be hard mounted to the frame, and that doesn't seem like a good design for our trucks.
As sope said, some people have gone to the frame, and it may work long term it may not. His truck is also modified (trimmed) so it is a bit different class than what I am going for. It just depends on what you really want out of it. Sope has done a very good job on his sliders, and it may be a great design that lasts for years. I just personally prefer not to tie into the frame for this type of setup.
Edit: Both the Toy and the Scout have less distance from the rockers to the frame than a K5. So they are applying less leverage than the wide body/narrow frame design of the K5.