crazy banana

Nice experiment and good job documenting it.
I love my "old faithful" reliable dwarf Namwah. Fruits every year and the bunches get bigger every year, too.
It would not surprise me if you will see an inflorescence on your plants soon.
Your experiment is interesting and possibly helpful for other members with marginal climates. One thing to take into consideration though when talking about cold resistance is to look at how long the plant actually was exposed to the cold. Here in San Diego I had four mornings in December with about two hours each were the temperatures dropped to 28F. All my plants looked similar than yours. However, I think if the temperatures would have been that low consistently over a longer period of time (days or day and night), the plants and especially the p-stems would be in worse shape if not completely destroyed.