I just took delivery of 600 sq ft of 5/8" bamboo flooring and on
unpacking it about 50% is warped.

The planks are about 3ft long and they're warped by up to 1" along
their length. The suppliers claim this is normal and that they'll be
fine once they're nailed into place. I'm not so sure that even if it
does install OK I won't find it lifting in a year's time.

Does anyone have experience or data on what's an acceptable amount for
the planks to be warped by?

Tim