The guy I used to train with that does over 6 plates for gm's showed me a way to do them, with a certain arch in your back, that takes the stress off the spine and puts it on the surrounding muscles, makes it easier to go heavy.
I haven't done them for 5 months, but did them this week, after deadlifting 4 1/2 plates for sets of 5, and still managed sets of 5 on the gm's on 305lbs. Dissto, whose also a member of this board, was spotting me.