I had the same Woodcraft ones that ZIM's running in that photo on my 2nd gen SV and in a low-speed lowside (back when the bike was a streetbike) it bent the hell out of that metal post that the slider mounts to, and it turned the engine bolt into a U as well.
When I built the bike into a racebike I switched to T-Rex Racing sliders (
http://t-rex-racing.com/catalog.php?item=58&catid=38&ret=catalog.php?category=38) after a recommendation from a WERA racer. They use a single long bolt that goes straight through the entire frame and engine, with two locknuts on either end to secure the sliders to the frame. The base of the slider is cut to fit into the indentation in the frame where the engine mounts so there isn't just a skinny bolt or post sticking out but the entire slider is "sunk" into the frame a bit for a very solid mount. They stick out about 1-1.5" past the bodywork.
I've crashed on them 3 times this season (2 on the right and once on the left), and it was only after the 3rd (and fastest) crash that the bolt bent slightly on one side (I was still able to pull it out of the motor without problem). The sliders have ground down nicely and definitely saved the rest of the bike from much more severe damage. Twice the bike has slid across the curb into the dirt and it didn't flip either time. Since the bolt doesn't thread into the frame or engine there's no risk of destroying the mounts, which is nice. I'm a big fan of these!