Apologies in advance for the long (and somewhat slovenly—as I’m writing in haste) post, but here’s my winter 2018-19 report for those interested in such things.
I’m in 6b Kentucky. Low last winter was 4F.
I protected figs by cutting them back to about 2’-3’, wrapping best trunks with fiberglass pipe insulation covered with paper tree wrap, bending/tying everything together to make a tighter package, surrounding with a cage, tightly stuffing that with straw (mostly cereal, but some white pine straw), and topping it with a mylar emergency blanket covered with more durable clear plastic. Where limber and low-lying branches/trunks were present, these were pinned to ground and bent to fit within the confines of the cages; these had a very high survival rate.
Nothing died to the ground—but Beer’s Black (a VdB-type) came very close. Mt. Etna types had very little to no dieback (regardless of where they were planted) and produced pretty well for their second year, despite the severe haircut. Improved Celeste in the open lost two-thirds of its pruned self, as did Ischia, LSU Purple, Longue d’Aout (which I scrapped this spring in order to replace it with a specimen without FMD symptoms) and whatever the finger-leaved thing Agristarts markets as “White Marseilles” is. Improved Celeste ripened some good figs starting I believe in mid August; whereas these others either ripened only a few very late (LSU Purple) or none at all. Olympian lost about 1/3 of itself (but bore some figs beginning in the first half of September) , as did another, older Improved Celeste—incorrectly identified as English Brown Turkey, but probably actually Edible Landscaping’s O’Rourke NOT. Regular Celeste had no dieback----it set figs but ripened none.
These were all out in the open. Other figs were planted in two microclimates: 1.) on a southern slope just above a little stream/partially filled-in pond and 2.) against an old concrete foundation. These experienced little to no dieback, regardless of cultivar. Among these were Lattarula, Yellow Long Neck, Improved Celeste and a number of Etna-types. Only IC and the Etnas ripened any figs; the others didn’t even produce produce figs. (The others, btw, were tissue cultures and this may account for shyness about bearing). The IC planted against concrete and which experienced no dieback ripened more figs and started earlier (by a couple of weeks—in early August—if memory serves) than the one planted out in the open which experienced more dieback.
A few observations:
1.) Those figs which experienced the most dieback had two things in common: a.) they were planted in an area with no microclimatic advantage; and b.) the straw inside them was very damp, especially near the ground and in the center. This may have destroyed the insulating properties of the “fig stack.” The moisture came not from above but from below—wicked up from the saturated ground. It rained constantly last winter and the ground was perpetually soggy. Will seek to prevent a repeat of this by placing some plastic at the bottom of my cages this year.
2.) The extra wrapping with insulation and tree wrap didn’t seem to help much. Wrapped and unwrapped trunks had a similar survival rate. This is one annoying, time-consuming step I will skip this year.
3.) In zone 6 microclimates are very helpful and probably a must for some cultivars. Big revelation, right? 
4.) If you can get things close to the ground, they’ve a better chance of surviving. For this reason, the low cordon method recently described by @hillbillyhort could be a good alternative for marginal zone fig growers, and I hope to experiment with it in the future.
On the whole I had a decent second fig year. Did run into some non-climatic problems—including SWDs (saw the males) and possibly African fig flies (which have been identified in Kentucky), and also some fungal issues which injured not only fruit appearance but also palatability in some cases. I hope to find solutions, however----and look forward to next season.
But before I get ahead of myself, I’ve got to get through winter again! We’re looking at a low in the upper teens next week, so I’ve got to get at it a little earlier than I wanted to. I’m going to do pretty much the same thing as last year, except no extra trunk wrapping and I’m going to lay some plastic at the bottoms of my cages in order to prevent or lessen the wicking up of ground moisture. If I have time I may try to wrap more of Celeste somehow; @hoosierbanana explained to me a while back that Celeste doesn’t bear well after heavy haircuts or dieback, and that seemed to be the case with this one. In fact, I’d really rather not cut any of the figs back so severely, but I’m really pressed in terms of time and limited in materials; heck, I’m just one harried guy on a budget with about 30 in-grounds. If worse comes to worst, those which set no figs whatsoever this season—including “White Marseilles,” Ischia and Lattarula—can just deal. I’m thinking about culling them anyway, as I have more figs than I can probably handle. Have a (healthy) LdA, three Rondes de Bordeaux, a couple more Malta Blacks, an Unknown Italian Yellow Westfield (reportedly similar to Brooklyn White) and Alma (which I don’t expect much out of in 6b—but I had one, so what the heck!) new in the ground this year.
Good luck to everyone this winter!