In addition to the ideas about the sheeting, the heat lamp, and the multiple feeders and waterers, I'd also think about putting in some distractions. If they are busy exploring and pecking at other things, they aren't pecking at each other.
Put in a tree stump for them to climb on and jump off.
Put some stuff like a few dirt clods for them to destroy, peck at and dust bathe in.
Also a dust bath is a good idea....either pile some dirt in a corner or put some in a tub for them.
Distractions, distractions. Whatever you can think of.
And one more thing I think I'd do - I think I'd prop a piece of plywood or something along one side. Anchor it so it won't fall down on top of them, but if you put it at an angle like half a tent the persecuted chicks can get under it and "hide" from the more aggressive chicks.
Hang a few apples from a string so they can peck at that. If you're worried about feeding that kind of treat too soon, toss in some small sand or gravel, or even regular chick grit right on the floor of their area. They'll have to dig and scratch for it, but they'll do it. Mine have been getting dirt clods, chick grit, scratch and treats since they were two weeks old and they've done just fine.
Stick in some thick branches or a couple of 2x2s for roosts at different levels. They love hopping from one to the other.
My chicks go from shipping to outdoor run with no heat lamp...I use a heating pad, a wire frame, a towel, and some straw. So from the time the sun goes down until sunrise they are sleeping. That's 8-12 hours of no pecking at each other. You don't need to heat an entire space with your heat lamp(s). They spend most of their time running all over the place and just warm up when they need it. Just make absolutely sure that the heat lamp(s) are secure! Don't rely just on the clamps. Good luck!
