If you're 100% certain that it's not a striper hybrid, then you'd probably be safe with following the white bass 10" limit. But, if there's a chance that it could be a striper hybrid, then you'd probably have to follow the 18" size limit.
You ought to call TPWD and ask them (and tell us the answer). It's an interesting question that's not really covered in the regulations.
Edited by Uncle Zeek (04/23/15 12:00 PM)
"Decency is not news; it is buried in the obituaries --but it is a force stronger than crime" ~ Robert A. Heinlein, 1952