I know this subject has been talked about everywhere but I think people are trying it all wrong. Just like with bananas if you don't know what you are doing and you live in a marginal area they will most likely die or you will have poor luck. I think we all need to try different varieties and see how much more we can push the limit with coconuts
In "The Coconut Odyssey" on page 38 under "Tolerance of Low Temperature" it says there are indigenous coconuts that deal with near freezing temperatures in Hainan Island off southern China. The other more exotic varieties die. I think this would be a good coconut to try.
In this video at the 6 minute mark he says his green malayan died in the frost but his yellow malayan did not. Seems like the Malayan yellow may be another good one to try, it is also available in the U.S..
All Natural Organic Green Coconut Farm in Miami, FL - YouTube
I also think the Fiji Dwarf (Samoan, Niu Leka) would be another good one to try. Its fronds are thicker and more compact, and its trunk is thicker than other dwarf varieties. Maybe that would help retain a little heat overnight in marginal areas.
I say keep your eyes out for something other than Jamaican or Hawaiian talls and grow them side by side and see which ones do a little better. The way I see it, one that can handle a few more degrees than another one may be all some people need.
Sorry for any grammatical errors I am sleep deprived for testing so I am very tired