I have recently seen "WARNING - MAY CONTAIN TRACES OF NUTS" on a pecan pie.
I have flown a single seater with a placard stating "Passengers fly in this aircraft at their own risk"
There was allegedly once an aeroplane at Boscombe with placarded "it is forbidden to crash this aircraft". I've often thought that Transair should market the latter.
In general terms, I'm not sure that placarded CG limits aren't pretty pointless too.
G