No one deserves to live with back pain for the rest of their lives just because some incosiderate toss SLF wants to load an extra 10kg in their bags. The 20kg proposal sounds reasonable to me.
I sustained a permanent back injury at 21 years of age while serving in the Army. Caused by heavy lifting in cofined spaces (trucks/aircraft) and made far worse by job requirements (parachuting, off road motorcycle riding).
I coped well enough to get through aircrew medicals but when I finally discharged I found it nearly impossible to get another job. I would always get through testing and interviews, only to be knocked back on the grounds that I had sustained a back injury in the past and they did not want to be liable for any re-injury. I eventually did get a decent job (by not informing them-doesn't pay to be honest sometimes) and have had no dramas.
As long as I keep fit I am relatively pain free and can do anything, but aerobatics are still a bit of a killer. If I couldn't work I would be stuffed, compensation is a joke and the thought of not being able to work when still young would be soul destroying.
The success of qantas and other airlines rides on the back (literally) of their operational staff. They should be looked after and should not have to break themselves just so GD can make a bigger bonus.