Well we're assuming the feathers have to be held together when in reality with the absence of any external forces they'd do it on their own, so I don't see the harm in assuming the case is massless (when it's in fact theoretical to begin with). Eventually, you would just have a feather planet with a brick core anyway, since all the other gravitational forces are essentially insignificant. Well, more insignificant than their forces on each other.
Just got done sampling two peanut butter pies, to die for. PB is def great, but it doesn't change the fact that so are pecans.
Y'know, it's not even the pecans so much as the gel stuff underneath- I don't even know what it is but it's amazing. The pecans add texture and a contrasting flavor on it, mmm. Something delicious.