Re: Good extrapolation
The distance from the center of mass makes a big difference in surface gravity. Neptune - in real life - has a mass 17 times that of Earth, but due to its huge diameter its surface gravity is a quite tolerable 1.14 g's. In college I laid out an idea for an SF story about Buckminster Fuller-type giant geodesic balloons that would be permanently stationed high in the Neptunian atmosphere, manned by scientists. The basic physics works out, given a permanent source of heat like fusion, and I assumed (on limited data) that the upper atmosphere of a cold world like Neptune might be more calm than that of Jupiter.
Later, I found out that someone else had the same idea and actually did something with the concept.