I recently approached the difficult task of trying to express the above in very simplistic terms. The results of my efforts are here:
http://www.DeepSouthDivers.org/homebc.html The article was designed to express the basic premise of "CofG" and "CofB" and how a diver would benefit from keeping the two points (which we all seem to agree on in terms of definition) as close together as possible. In an effort to express why I chose a certain gear configuration, the article is also slanted to explain (in very general terms) how the gear I chose does that, exactly.
I've had a slew of reactions to the article; most of them positive, but some of them arguing that many factors are not accounted for in the oversimplified illustrations.
Some of the variables that were not accounted for:
1. Placement of "trim weights" in "standard" BCs.
2. Changes in CofB due to emptying tanks.
3. Changes in placement of CofG due to gear such as heavy fins, ankle weights, etc.
4. Changes in placement of CofB due to wetsuits of different thicknesses.
5. Placement of "P weights" or "V weights," which skew the CofG.
6. Tanks of different buoyancy characteristics.
No doubt all of these arguments are correct... That is, ANY variable is likely to change the "overall picture" of where the CofG and CofB are, and different techniques need to be utilized to achieve close CofG and CofB.
...But that's not the point of the article. The point of the article isn't to express an exact measurement of every gear configuration that a diver might choose, it's to express the idea and enable a diver to estimate his/her own positions of the CofG and CofB so as to "tune" them close together.
No matter what the gear configuration is, even the diver's breathing will change the position of the CofB to some degree. A full breath will make the CofB move towards the diver's head, while a good exhale will move the CofB towards the diver's feet. In DIR-F (mentioned only because your question specifically pertained to the dive style), negatively buoyant fins are recommended so as to allow the diver to change the position of their CofG simply by bending their knees. Bring the fins closer to the butt, and the CofG moves towards the diver's head... Straighten the leg, and the CofG moves down the diver's torso - slightly. This is how a DIR diver can change their attitude in the water without finning or moving their hands.
That said, you'll have to figure out where your own CofB and CofG are, based on all of the above information. Keep in mind that the naked body has it's CofG much lower than it's CofB... Due to the massive buoyancy of the lungs - which changes about 9 pounds from inhale to exhale. This is why they make "standard" backplates as 6 pounds... It is a nice "medium" for offsetting the buoyancy of the lungs, thereby making the body more "balanced" in the water.
Hope that helps.