Bass, Saijo has been growing at the Wye persiimmon orchard for many
years. One of the trees recently died but there is still one left.
I would say it is hardy to zone 6. My own Saijo has taken -2F
without problems. I don't recall how big the Wye tree is but the
Spring 2006 Pomona gives the sizes of all the trees there.
On a related topic, I visited the Wye persimmon orchard last weekend
and have some extra scions of some varieties. I can mail them to
anyone interested for the around $2 postage. Send me an email if you
are interested. This orchard was written up in the Spring 2006
Pomona so look there for more information. These varieties have all
survived 25+ years in Maryland and so are good candidates for zones 6/7.