very good advice here from: karen1, irish, sugarbeth, jenseits , and others.
how perfect it would be to have an indoor area that size. you should have no trouble at all, with your training.
my sun, tiki enjoys free outdoor flight, and soon my GW, ruby will.
once you have it perfected, til its a conditioned reflex, you will have no problem outdoors.
the indoor part of tiki's training, was just my apartment. you should make great advances with that larger space, without the fear and adrenaline (SP?) that goes with the first few long distance flights, that most of us must try outdoors.
keep us posted.