I'm considering buying the tube to do what you have done. One thing though. The price is 37 GBP on blizzardsurvival.com, an underquilt on ddhammocks costs 75 GBP. So IF I were to buy 2 tubes to be able to camp whenever I wanted, the price would be the same.
Don't really know what my question is, just trying to find the best and cheapest option to be able to go camping in march in Sweden. Average temperature is 1 degree Celsius during that period here. Perhaps I have to invest in an underquilt.