I was a bit late last year protecting, but I did something like the below with a slight variation. Here is what I have done to my three largest butias for this winter. After tying up the fronds, I cut the top and bottom out of 55 gallon plastic barrels and slid them over the palms. I then placed either a 250w heat lamp or two strings of C9 Christmas lights around the base of the palm. Next, I wrapped all three with heavy duty frost cloth. I used Thermocubes that turn on the heat at 20F and off at 30F. I am hoping this will provide enough protection for them. I will cover all three with a tarp if temps get down in the single digits.
With frost cloth added:
I hope this works!!!