Being a tropical climate camper, I can sympathize with your issue. Even though I see no lower teperature than about 75, I can understand why keeping warm is a concern. A low of 50 is a lot different than the lows you are expecting.
I personally think that if you are seeing at a worst of 50 degrees, you will be perfectly fine with laying on your fleece blanket and a pad of some kind. that would be good to a relatively lower temp. I personally think it's a little overkill, but good luck with your decision.