Bottle jacks without saddles
I've been considering getting one of those hydraulic bottle jacks (probably from HFT) to replace my screw-type OEM unit, mainly for speed. However I notice most bottle jacks seem to just have a small cap on the end of the piston, and no saddle. How do people manage to lift vehicles with these things? I could see maybe using it against a flat surface (such as the bottom of the frame), but certainly people aren't jacking against axle tube round surfaces with these? That sounds like it would be dangerous without even a small saddle to make sure it's well-centered on top of the jack.
What am I missing?