That's me who did the recommandation of the three fingers mitt 5mm, they are extremely warm but they are thick so you can start feeling some pain in the upper arm after an hour but normally in that cold temp it is enough to kite for one hour
Going to Cuba soon, that will help for sure
PS : I have the Dakine Titanium mitt too but they are not really warm, at least not enough for here in Quebec! No comparison with the 5mm mitt mentioned above.
Send me a PM if you want more info, I could check to be sure of my exact model of mitt. I have never find something that warm.