How are you using these hockey pucks as jack pads? Obviously you're cutting a slot into them for the pinch welded seam, but are you just placing them onto of the jack pad, or do you cut them to a size that fits into your particular jack pad? Does this really only work if you have a larger jack pad? My partners Corolla has those super-annoying pinch welds and if I avoid them during jacking by placing the jack under suspension components I then find myself with nowhere to place an axel stand. I only have a Hilka 3ton jack, and the jack pad on it cant be more than 6cm or so - so substantially smaller than a puck!
Yeah I just sit them on top of the jack pad, or the jack stand. Yes, they are larger than the pad, but they are dense rubber, so they deform a little under the weight of the car. They don't to sit in the "cup" of the jack, it just presses into the bottom of the puck.