I just worked the W&B numbers. For an RV-8/8A with the 180hp IO-360 and Hartzell CS prop, one PC-625 battery mounted forward, and one PC-625 in the normal aft position yields a nice W&B. This is what I did on the new RV-8 project.
I mounted my forward PC-625 in the forward baggage well. I was never a fan of batteries mounted forward of the firewall.
In my first RV-8A I mounted one PC-625 in the forward baggage well, and one on the left side just aft of the firewall. The W&B was workable but 25 pounds of lead shot in the baggage compartment made solo flying better.
If you are interested I can provide photos on how I mountd each battery, and the power distribuion wiring instruction. Just PM me your email address.