In my herd that is NOT giant. Most of my does are 9.5 lbs. or larger. I have a 12 lb. buck right now and these are purebred Rex for at least 9 generations, no FG or other "giant" breeds. I don't have much problem with sore hocks, but I would cull for that. All my rabbits are in standard wire cages and I use plastic lattice panels that you can buy as 4'x8' sheets @ home depot. I cut into 12"x12" and in the grow out cages I have started using them 12"x24" which I like better. It takes longer for the bigger sitting boards to get "eaten" since many of the bunz do like to chew on them.
I think that you can select for size and have "giant" Rex within a couple of generations if you only keep the largest for breeding.