Yup agree just a wing can make that ballast moving easier that's all
Trim is mostly psychological. Unless you are weighted catastrophically poorly, or hugely overweighted, then you can trim out anything. Put a diver with stable, understood trim in a BCD and a single cylinder, or a twinset, or indeed a rebreather, and they will understand where they are in terms of trim, and indeed be able to trim "most" of those configurations out.
Moving a Kg or so up and down your body will make no difference, especially if it is your legs that are dropping. Sounds like you are fighting with too many variables. Like some of the others I would recommend a day with myself or Mark Powell. If there's one thing that needs fixing you can learn it on the internet, but in this case you have lots of variables, and changing one is going to affect the others. from what you describe I don't think trim is actually the issue here, I think buoyancy control is. Sort that out, and then work on your trim.
Start with a read of this article, and give it's suggestions a try Fine Tuning Buoyancy | Articles | Resources
Having a break from teaching divers.
Air rises in water, the air in a BCD, wing, or plastic bag will be at the highest point it can in that particular container - just because a BCD has places at the front for air to go does not mean air will stay there when you are horizontal (where is the facepalm emoticon?). Ergo if you are horizontal in the water in a BCD then the BCD will also "suspend" you....... If you are slightly head up then all the air will be around the shoulder area regardless of wing/BCD FFS :omg:
To the OP, think of your buoyancy system as a newly fitted tyre on the car, the technician puts the wheels onto a spinner and balances it with carefully placed weights - this is what you need to do with your BCD/Wing and the weights you use, and only practise and observation from friends will get it right.
Edit: Just seen better posts by Bantin and Janos.
Last edited by Stevie H; 06-01-2013 at 10:04 AM.