Just for reference.
Maximum designed wing flex, as measured at the tip, prior to wing skin deformation, while in flight...
B707-320B (advanced cowl)
11 feet up, ten down.
Douglas DC-6B.
Six feet up, six feet down.
Wing bending relief, at work.
Source.
Senior design engineers.
In the latter case (DC-6B), chief project engineer, a very close relative.