I have a pair of 3 ton and a pair of 6 ton. I sometimes have trouble getting the car jacked up high enough to get the 6 ton stands under the rocker panels. Using pieces of industrial rubber over the "V" on the stand keeps it form scratching and seems to make it quite stable. I have a piece of I beam I use on the top of the saddle. I made a mistake and used a 4x4x8" the tall way and dropped my wife's Honda onto the jack, crunching the oil pan. I had jack stands under it at the time so it "caught" it on the way down. It's still up on the jack stands. One stupid mistake can cost a lot but jack stands are very safe. If you have (4) 6 ton jack stands holding up a 5000 lb car you have nothing to worry about. Always shake the car to see if you cna move it. IT should not budge. I tend to use extra jacks, wheels, I-beams and ramps for security.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si