Mark ~ good idea on the mason jar, rather like a cloche . In this zone, we would have to be very careful to remove it on sunny days or the plant would be toasted. lol
Bev ~ I think the frost cloth is probably similar to your N-sulate cloth. It is far lighter weight than the shadecloth I have. Almost like a pellon fabric.
For me, I'd be afraid a plastic liner on the succulent pots would allow them to remain too moist in this zone.
Tee ~ don't you hate when that happens. Seems my laptop is far more sensitive and eats what I type all too often. Wish I could retrieve it many times. You get far, far colder there so I am curious, have you ever lost any succulents in that sheltered area?
Does anyone here withhold water in winter for their outdoor succulents? Or protect them from rains?