Well, the magenta is basically to counter the spill, and you don't use much of it.
You should look into multiple sheets of green fabric if the one you have is too narrow. You can also get a roll of 9' x 36' greenscreen paper for about $50, roll it out, use it, and roll it back up. There's also greenscreen foam which doesn't crease the way paper or cloth can.
I'd suggest multiple light sources to get the green even, ideally one below, one above, and one to either side.
If you want easy to transport and set up lights, try china ball lanterns, as they collapse flat.