Archerfish, yes, conventional wisdom says NOT to jack on those "pinch-weld" seams, as they constitute a "knife-edge", and they could easily be bent away from plumb. That's what your rubber blocks seek to prevent. And I, too, have a set of rubber-faced wooden blocks with a sawn slot in each block to "miss" the pinch-weld seam...
However, I can't use them on my Mazda6. Mazda6's have what Mazda calls a "sill moulding, i.e. essentially a plastic moulding that is affixed to the rocker panel, and which theoretically serves to protect the rockers from rock chips... If I use my blocks, then the car's weight is taken NOT by the pinch-weld seam (on-edge) but by a combination of a squished, compressed, cracked sill moulding, and a squished, compressed, cracked under-car aero panel.
Neither alternative is acceptable to me. Instead I do the following:
The pinch-weld seam comprises three (3) thicknesses of sheet metal, and one of the three gauges of sheet metal is ultra thick. Also, a portion of this pinch-weld seam has the most-outboard sheet metal folded over top of the seam, i.e. folded inboard. I judge these parts of the pinch-weld seam as being very strong and NOT susceptible to damage due to lifting the car. They are near-to or part of the cars' jacking points. Accordingly, I have fir blocks (Douglas Fir, wood) blocks, and I support the car at those folded over locations with these wooden blocks and my jackstands. I could improve the safety by taking the barest skiff of a saw cut down the centre of each block, maybe the width of two saw blade kerfs. The wood "gives" a little, and does not break the paint.
That's my solution. I lift on the pinch-weld seams at those locations.
Oh one more thing... If you are using deep V's or slots on your rubber jack pads, and if said jackpads contact the actual rockerpanel (ultra-thin) sheet metal... I'd bet you'd bend or crease said sheet metal easily. It's really, really thin-gauge. Stay away from it!
Others: YMMV...