Fixing a Ladder for hanging pots in the Kitchen?

I have a problem where i am trying to fix an old decrotive ladder to the ceiling of my kitchen, the problems i face are 12' ceilings and the weight of the ladder even without the pots would be in excess of 15kg, also due to the age of the house it is almost impossible to access the internal roof cavity as the manhole is about 300mm sq, so i cant install booker rod from the inside of roof cavity, i cannot find any hooks with a long enough thread to thread into the roof battons, does anyone know of any hooks with a long thread say at least 75mm that are robust enough to handle about 20kg, i would love to finish this project, so that the cook is happy.

Matt
June 2008