Good points. Obviously, jacking on a hard, flat--preferably concrete--surface with a good floor jack is the best way short of a lift. Even that, however, is not without some risk (theoretically, even a lift has some risk). Also, the jacking situation is only as good as the surface you're jacking on (heh). So, we're back to our concept of 'risk management.' I take a 4K mile road trip every year, and don't shy away from any road except dirt and gravel, no matter how far from help, so I have to be prepared for any eventuality. The boot is packed with spare tire, tool box, spare parts, a car cover, extra oil, brake fluid, flares, towels, toilet paper, paper towels, a tow strap, jumper cables, a spare inner tube, rope, bungie cords, laptop computer, portable compressor, first aid kit, collapsible water carrier, Bentley shop manual and a box of cigars. No room for a floor jack, and the Shelley jack--I have a complete one, special for forum members at only $50,000--is pretty much useless.
That leaves a scissor jack as the best option for me. I bought a Torin 'Big Red' jack for the Healey, and put the geared jack in my Mustang. The Torin is not geared, like most scissor jacks these days, but I thought hey, a Healey is a light car, what could be a problem. Well, when my fuel pump started acting up in the middle of the Nevada desert outside Ely I pulled over to swap in the spare (which had some issues too, but that's another post). I quickly found out that although the Torin could lift the car--at least a portion of it--it was much more difficult than the geared scissor jack. Add to that the sloped, dirty, gravelly condition of the road's shoulder and I felt very nervous cranking really hard on the handle whilst the jack twisted and moved under the car. The geared scissor jack--sitting comfortably in the boot of my Mustang 500 miles away--worked much better, with much less effort and less potential for twisting its way out from under the car (it's also of more robust construction).
When I got home I located and bought another geared scissor jack, different brand but all but identical to the older one (think just the brand name and some other minor things changed). My original geared jack is now back in it's rightful place. Anyone want an almost-new, Torin 'Big Red' scissor jack? I'll throw it in with the Shelley.