Tied onto ribbon isn't very "adjustable" is it? You'd end up with a huge gap in the tulle once they started growing. Elastic is more "adjustable" than ribbon, IMO. I only make elastic ones for this reason. I can't think of a way to make it adjustable without gaps? I'd love to know if there is a way!
ETA: Found this on etsy. If this is what they mean as "adjustable", I don't agree. http://www.etsy.com/listing/29383071...t-toddler-tutu