I lined the inside of my 260 with thin sticky neoprene sheet,stops balls rattling around whilst running .Tested it before and after lost two balls in capacity.
So nothing to worry about.
This stuff I had some left from another project (LV1 EMC kit) http://www.pinbax.com/index.asp?selection=detailed&uid=32363&cg=1&mc=4&cct=9&sc=5