Keep in mind that this is just my opinion, but: Why do most certifying organizations teach proper weighting as becoming neutral (or floating with about half your mask submersed) when this will lead to your being positively boyant at the end of the dive? I like to be slightly overweighted at the begining of the dive so that I am neutral at the end of the dive when my tank is empty. If you are neutral at the begining of the dive there is the possibility that at the end of the dive you will be positively boyant and that will make a safety stop difficult at best. Again this is just my opinion and my way of doing things. Use at your own risk.