The F4 wingtips cracked from vibration, not G. However, G set up the
vibration. Flying close when when lead was doing acro one could see
the wing tip vibrating as the tip vortices did their 'Karmann trail"
thing. The 110v 'thin filament' tip lights used to fail in a jiffy
until they rewired then for 28vDC 'heavy filament' bulbs.
We had an F4 at low altitude peg the G meter both ways when the tip of
the 600gal centerline came off as the pilot (Stormy FAC) dodged a SAM
coming right in from 12:00. Later a second F4 had the tip shot off his
centerline tank and the Gs piled on the same way. Turns out the blunt
nosed tank sets up severely disturbed airflow over the horizontal
stabilizers.
Both aircraft checked out okay except lots of 'bubble gum' was needed
to reseal the bottom of the internal wing tanks.
Walt BJ