A tire boot should be non-stretchy material, not a tube patch or piece of inner tube, though that would be better than nothing to get you home in an emergency. I've had dollar bills and other patches (piece of sewup works nicely) inside a tire I've ridden on for months. If I can boot the tire and not have a bulge or spread-open gap at the slit with full inflation, than I'm happy to keep riding on the tire.