Blueskies wrote:
How about cork? Probably too heavy...

And absorbs water. If it wasn't heavy when you put it in, it will be
after you fly through the first cloud. Whatever you use, make sure it is
HYDROPHOBIC

(a word I learned about in RAH)

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber