Call it redundant, conservative, belt and suspenders or just paranoia, but when I get under a vehicle for even an oil change I use both main and backup supports. I use a combo of supports from a choice of four jack stands, two hydraulic jacks, a van screw-type bottle jack, two ramps and have even used the Firebird's bumper jack as a final backup. The Firebird is so low and I need XL clearance to get under it so that car has to be raised quite a bit.