Charging circuit - reduced load on ammeter circuit

Have you not actually tried it?
No. Tim tried it. I did the parallel feed. That keeps the ammeter seeing everything the battery is doing. I even moved the MSD's power supply over.
If Tim doesn't answer here, you know where to find him. He can tell you exactly how much charging, if any, he saw on it.
What he did see was discharge. That will continue to work pretty much as before.