Blacky wrote:
4 x 3lb weights as a start and get a rubber belt to help keep weight in the correct position. You should be able to just float on surface without having to work at all. Don't over weight yourself and learn good duck dive technique.
I would like to add that the weighting depends on the depth you dwell at.
I try to be equalized -non buoyant- at -12mt, in order to move about at -15mt with ease (just slightly negative) and be strongly buoyant where it counts, at -8mt or less (less effort during the last part of the dive, when shallow-water black-out may set in).
Bottom line: with setting similar to yours (5mm wet-suit and 68 Kg) I wear 4 Kg of weight.
If you dwell at a shallower depth, you would need to bring more weight, of course, but
still ensure to be strongly buoyant during the last few crucial meters of a dive ... this is crucial for both oxygen conservation (to avoid a black-out) and rescue (in the unfortunate case of a black-out).
One last tip: wear the rubber belt pretty tight around your hips -hence pretty low- to free the diaphragm from restrictions and avoid the belt moving around with the shrinkage of both body cavities and wet-suit caused by pressure.