I would not think all that would be needed in a true zone 9a. Mine(orinocos, ele ele, ice cream) made it through 22F and several 27f-29f nights last winter with no protection.

Sure, I lost the leaves, but none if any of the pseudostem. I left the dead leaves on until spring as it provided some extra protection and collected frost.

Not sure about cold hardiness of williams hybrid.

Hello porkpi,
Thanks for your opinion, and it was very nice to know that
Orinocos, Ele ele and Ice Cream survived through 22F with
no winter protections at all. What was possible in zone 8
should be possible in zone 9a.
In fact, Sikkimensis and velutina have overwintered out-doors on the ground without any winter protections.
So I will try it also for Williams hybrid of which hardi-
ness is about the same as Ice Cream.