I would concur with the previous comments [use both], but found with practice that an inside thermorest was viable over time altho not perfectly stable – I do have to adjust. I have also used excess clothing/coats and traded thermorest with wetsuit to reasonably good effect. Extra tarps for ground/privacy/wind/and extra driven rain protection are very useful, gear ‘storage’ is under the hammock – but not great.
I have an old hennessy camo safari [it’s quite large] . . .. and there is just nothing like waking up in the morning to an expansive view out the hammock while hanging over terrain that a tent would never be able to be used over. It’s an adventure walking thru the forest and having all sorts of different and undeveloped locations that can now be used rather than requiring flattish smoothish ground. I was sold on this aspect the first time I used it on a slope near the top of a small cliff – I can still remember the scene out the expansive netting, waking up in the morning after setting up in the dark. Glorious.