@ Mark B.----I have had Chicago Hardy in ground for a couple years now in Kansas. We hit below zero every year, even for brief periods. Lots of windchill here too. My CH is right up next to the south side of the house. There is some die-back each year, esp. if I take late cuttings like I did last week (yeah, I know---kinda dumb)...but it rebounds like gangbusters. So does my LSU purple. They are about the same size as your trees...about 3 + feet. I have never covered them EXCEPT once the leaf buds start swelling in Spring, and I know we will have late freezes. Then I throw a tarp loosely over....
The only figs I have ever killed in winter were those I overwintered indoors (not the garage---INDOORS)---I actually underwatered and killed my RdB :-(. It also suffered from maladjustment when I put it outside in Spring...it died in a cold snap in pot. An old Sicilian fig grower in NY told me the best you can do is not baby them, to put them permanently in ground as soon as they have a good root system, either dormant in Fall or in Spring after freeze risk---let it acclimate. That is what the first Italian immigrants did in NYC...and now those fig trees are HUGE. If you are really worried, take cuttings when it goes dormant. That way...if it dies, you have rooted cuttings by Spring as back-up.
cheers!