The BCD that I used was an old Sea Quest, that allowed for integrated weights at the sides and it had space around the tank strap for an additional two weights. We put 2kg in each quick-release pocked and 2kg on each side of the tank.
This configuration obviously shifted the weight distribution quite significantly. It was nice not having weights digging into my kidneys but when carrying / lifting the BCD the additional weights caused the BCD to push down on my shoulders.
I felt the effect of the weights immediately in the water. Trying to remain upright at the surface was a little more tricky as the weights kept wanting to pull me back.
Once I got underwater it took me 5-10 minutes to become accustomed to the new distribution. However, for the remainder of the first dive and for all of the second my buoyancy and trim control was great. It definitely made a difference and I was able to hover quite successfully for almost 3 minutes (while doing the safety stop in a cave), the only issue was the swell.
It’s definitely worthwhile to consider carefully the placement of your weights.