DD had a XENO a few years ago same issue. She said it rattled from pretty much the first time she swung it. Never saw anyone umps address it and quite a few girls were using them back then. Most on her team now have Demarini, Ghost or LXTI have a Xeno that has a very slight rattle. I know that technically it is illegal but how thorough are the umps and what is the chance that it will be tossed out?