I do not normally fly deltas but I flew an Emma Kites mylar delta http://www.emmakites.com/new-9ft-stealth-mylar-delta-kites_p276.html
today for the first time.
I do not know if it is a copy, or if it is durable or if the quality control on these kites is reliable.
It looks fine to me.
What I can say, is that without a tail, the kite rose smoothly and then remained fixed as if pinned to the sky!
Unfortunately, high flight angles are not my preferred choice.