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Na, I've slept out in summer in the hammock in just a sleeping bag and been fine. Wasn't a particularly hot night but it wasn't cold/raining either so take that as a very small sample size. Testing is best ting, even if you just go out for an hour and read your bike one night, you'll get a good idea. But imo don't both taking it because you can always layer up inside your sleeping bag if you're cold.
In terms of temp I don't think you'll need any extra insulation. Can always chuck some clothes under too