You'd only be off by a factor of 3 instead of 4, then.
In any case, comparing it to a solid ball isn't so useful. Even the idea of "density" for something that is dispersed as small particles isn't too useful; proportion of mass is really the only useful metric.
In any case, comparing it to a solid ball isn't so useful. Even the idea of "density" for something that is dispersed as small particles isn't too useful; proportion of mass is really the only useful metric.