As you say, you can't jack under the axle because that won't relieve the load on the springs.
However I would never jack on the axle. I always use the rear crossmember with a wooden pad to protect it.
Newer cars have the rear valance partly covering the crossmember but I believe there is still room.
Then put prop stands, again with pads, at the outer edges of the crossmember and lower the jack onto them.
I use very heavy duty prop stands with a bigger base area and then move the jack out for easy access.
