Hello:
Best to go to 33' and see if you are positive or Negative as far as buoyancy is concerned. If you still float up at 33' add a 1 lb and repeat. Everyone's body is different, and just saying all you are wearing is a vest, may not help with the actual weight determination. Grab your Gun, Low volume mask, put that vest on, and check that buoyancy. Neutral at 33 feet should be you goal, unless you are diving in very Shallow water.
Bruce
bruce nailed it...find the weight you need, then spread it around until you are most comfortable or are naturally oriented as you want to be.
Mickael- email me : phorbinn @ msn.com. I think Id like to try a vest