How much does weight position matter?

[tigerhawk]

I usually dive with about 18# in a pocketed weightbelt in FL and the Caribbean - this has worked for me for years. Last week I was on a cruise and made 2 day trips. In Cayman, 18# on a belt worked perfectly as I expected. The next day in Roatan, they used integrated weight BCs - put 20# in the BC and I could not descend at all - ultimately needed 24# which seems ridiculous. The boat captain kept telling me weight is weight and it doesn't matter how you wear it - but I have no other explanation for my difficulties other than weight position. I usually wear my weights near the small of my back - and of course the integrated weights are up around the front rather than behind me. Does weight position matter? Could my difficulties really be due to using an integrated BC rather than my usual weightbelt? Or are there other factors at work? The jacket style BC seemed to fit snugly enough - no loose places to trap air. It was a little longer than my usual BC - I am a 5'4" woman and this was a man's medium but I had worn a man's medium the day before in Cayman with no problems. Really interested in all your comments.

[Mako]

Dear Tigerhawk,
The weight position does not matter!
What matters your buoyancy is: your body + equipment total buoyancy.
You mentioned that you where not using the same equipment during these different dives, this is where the difference was! a different wet suit, BC or tank can easily make a difference of a few kilos.
My advice is every time you use a different equipment once in the water make a short buoyancy test before the descent.
When your BC is empty of air and you take a normal breath you should be emerged until your eyes. When you exhale the air in your lungs you should start to go down. Do this test and adjust the quantity of weight before you start the dive.
Please note with an aluminum tank, care to be a little negative, once the tank reaches 50 bar (725 PSI) it will start to have a positive buoyancy and slightly pull you up
The water: fresh water, salt water and quantity of salt in the water has also influence, in the Red Sea you will need 1-2 more kilos than in the Caribbeans. But this was not the reason of the difference in your case.
I hope this helped, otherwise don't hesitate to ask for more details.
Wish you lots of great dives.
Mako