We have (2) 8D AGM batteries and a group 24 AGM on the Starboard side. The port side has a couple of lead blocks for compensation, although I don't know their actual weight. Obviously, not ideal to be adding non-essential weight to the boat but it keeps us on an "even keel." We bought the boat used and it was this way at the time. I don't know if this is usual, but it makes sense not to be running parallel battery cables from both sides of the boat just to create balance in that manner.
Anyway, you could consider 'dead' weight such as this.